JP4095937B2 - Method and apparatus for protecting buried structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a buried structure security method and a security device, and more particularly to a security method and a security device for reducing an AC induced voltage of a buried structure.
[0002]
[Prior art]
As an important security measure for maintaining and managing buried structures, there is an electric corrosion countermeasure. The main causes of electric corrosion that buried structures receive are due to stray currents such as leakage current from rails of DC electric railways, DC interference caused by electrical equipment related to cathodic protection (electrical protection), and high voltage of power Some are caused by AC interference caused by AC induced voltage from AC overhead power transmission lines or AC electric railways.
[0003]
Among them, there are roughly two methods as a cathodic protection method (a galvanic protection method) which is an active countermeasure against electric corrosion due to stray current or direct current interference. One of them is a method called an external power supply method, in which an external electrode installed around a buried structure to be protected against corrosion is connected to this buried structure via an external power supply, and the external power supply This is a method in which an anticorrosion current is caused to flow into an embedded structure from an installed external electrode via an electrolyte such as surrounding soil by an applied voltage or current. Another method is a method called a sacrificial anode method, in which a sacrificial anode made of a metal having a negative electrode potential with respect to the buried structure to be protected against corrosion (for a steel pipe, an Mg electrode, a Zn electrode, or the like is used). .) Is installed around the buried structure, and the sacrificial anode and the buried structure are connected to each other by a conductive wire. This is a method in which an anticorrosion current is caused to flow into the buried structure through an electrolyte.
[0004]
Further, with respect to AC interference, the AC induced voltage increases as the parallel distance between the buried structure and the high-voltage AC overhead power transmission line or the AC electric railway is longer, or the electrical insulation of the coating covering the buried structure is higher. Further, the smaller the coating defect area, the higher the AC current density causing AC corrosion from the defect. Therefore, in recent years when there is a high tendency for parallel laying of lifelines, and the electrical insulation of coating materials used for buried structures has become high, even if there are small defects in the coating, There is a risk of corrosion, and electrolytic corrosion due to AC interference is becoming a serious problem in the security of buried structures.
[0005]
Such security measures against AC interference are performed by reducing the AC induced voltage of the buried structure. A simple method for reducing the AC induced voltage is to disperse or locally install a metal electrode (for example, an Mg electrode) having a high potential on the buried structure on the buried structure, and to bring the AC induced voltage to the ground via this metal electrode. There is a way to escape. In the case of a buried structure that has been cathodic-protected by the sacrificial anode method described above, the sacrificial anode is usually covered with a low-ground bag to increase the generated anti-corrosion current, and the ground resistance is low. As a result, the sacrificial anode itself can be used as the metal electrode to reduce the AC induced voltage.
[0006]
On the other hand, for buried structures that are cathodic-proofed by the above-described external power supply method, a method for reducing the AC induced voltage using a low-grounded object around the buried structure has been proposed (see Patent Document 1 below). . When laying pipelines such as gas conduits underground, steel casings and earth retaining sheet piles are often installed around the pipeline laying area during the laying process, and these are bare metal bodies. Since the surface area is large, it can be a low grounding object. This proposal reduces the AC induced voltage of a pipeline by electrically connecting a low grounded object such as a steel casing or a sheet pile to a pipeline that is an embedded structure. Also, connect a low-grounded object and the buried structure via a surge protector (impact protection device), and if the potential of both is below the set voltage, the AC current is conducted and the DC current is cut off. It is also shown in this proposal that current and direct current are made conductive to avoid a decrease in the anticorrosive effect on the buried structure to be cathodic protected, and at the same time, an impact protection measure is taken on the buried structure.
[0007]
[Patent Document 1]
JP-A-9-292100
[0008]
[Problems to be solved by the invention]
In the case of using the sacrificial anode itself as a metal electrode (Mg electrode, etc.) for reducing the AC induced voltage for the buried structure that has been cathodic-protected by the sacrificial anode method as a countermeasure against AC interference of the embedded structure. In a situation where there is a large amount of stray current due to the presence of a rail of electric railway near the sacrificial anode, the sacrificial anode works to attract the stray current, so there is a coating defect in the buried structure. As a result, a corrosive current having a high current density tends to flow out from there, causing a problem that electric corrosion due to stray current is induced.
[0009]
In order to cope with this, a backflow prevention means for blocking a direct current from the sacrificial anode to the buried structure through the lead wire through the lead wire electrically connecting the sacrificial anode and the buried structure (from the buried structure via the lead wire). In some cases, a back-flow prevention means is inserted to sufficiently reduce the AC induced voltage mainly composed of 50 Hz or 60 Hz. It will not function as a measure against AC interference.
[0010]
On the other hand, when an AC interference countermeasure using a low-grounded object like the conventional example is taken against an embedded structure that is cathodic-protected by the external power supply method, the embedded structure (pipeline) and the low-grounded object Air gaps (steel casing or sheet pile) are filled with an electrolyte such as air mortar, sand, or water, and in an embedded structure subject to cathodic protection, the anticorrosion current from the external electrode is embedded from the low-grounded object via the electrolyte. It flows into the coating defects of the structure.
[0011]
However, when the surge protector inserted in the connecting conductor between the low-grounded object and the buried structure is damaged or when a voltage exceeding the set voltage is applied, the low-grounded object and the buried structure are short-circuited. It will flow into a certain steel casing etc., and will cause the fall of an extreme cathodic protection efficiency. Furthermore, when a lightning containing a high frequency component is received, an effective impact protection effect cannot be obtained with the surge protector alone, and a surge current containing a high frequency component flows into the buried structure, causing damage to the buried structure body. Can cause significant damage.
[0012]
In addition, in order to confirm that the buried structure is at an appropriate level of cathodic protection, a probe simulating a coating defect is installed at a predetermined interval inside a low-grounded object such as a steel casing, and the probe current density is set. (Probe direct current density and probe alternating current density) are measured and checked against the cathodic protection standard. However, in this situation, if there is no coating defect in the embedded structure, from the external electrode The flowing anticorrosion current flows into the probe after flowing into a steel casing or the like which is a low grounded object. In this case, since the surface area of low grounded objects such as steel casings that come into contact with electrolytes such as soil is overwhelmingly larger than the surface area of the coated buried structure and the probe, the anticorrosion current density is applied by the low grounded objects. The ground potential of the low grounding object is smaller than that of the buried buried structure and the probe, and the value of the ground potential of the low grounding object is on the positive side of the ground potential of the buried structure and the probe.
[0013]
However, if the cathodic protection of the buried structure is not effective for some reason and it becomes naturally corroded, the ground potential shows a high value on the negative side if a low-grounded object such as a steel casing is in clayey soil. (For example, -800 mV: saturated copper sulfate electrode potential reference) On the other hand, since the buried structure and the probe are in contact with an electrolyte such as air mortar, sand or water, the ground potential is close to the positive side (for example, -400 mV). : Same standard). In this case, if the grounded object and the buried structure are electrically short-circuited, and there is a coating defect in the buried structure, the ground potential difference between the two and the grounded structure is used as a driving force to prevent corrosion from the grounded object to the coating defect. Current flows in. If a low-grounded object such as a steel casing is at a long distance and another coating defect is located at a remote location, the corrosion protection current will flow out from this location, resulting in a new corrosion risk. Occurs.
[0014]
An object of the present invention is to cope with such a situation. For example, AC interference countermeasures can be taken while maintaining an effective cathodic protection state regardless of the sacrificial anode method or the external power source method. However, an object of the present invention is to provide a buried structure security method and a security device that can cope with impact protection against lightning currents in a wide frequency band including high frequency components.
[0015]
Furthermore, for buried structures that have been cathodic-protected by the sacrificial anode method, it is possible to avoid the risk of corrosion due to stray currents, while at the same time providing a sufficient function as a measure against AC interference. The buried structure and the low-grounded object provided around it are not short-circuited, and the AC induced voltage can be reduced by using this low-grounded object. It is an object of the present invention not to induce electrolytic corrosion in an embedded structure even under natural corrosion conditions where corrosion protection is not effective.
[0016]
[Means for Solving the Problems]
In order to achieve such an object, a buried structure security method and a security device according to the present invention are characterized by the following claims.
[0017]
The invention according to claim 1 is a method for securing a buried structure, wherein the low grounding is electrically connected to the buried structure and a low grounding object installed around the buried structure via an electrolyte. All direct currents directed from the object to the embedded structure through the conductor are cut off, and direct current from the embedded structure to the low-grounded object through the conductor in accordance with a potential difference between the embedded structure and the low-grounded object The high frequency alternating current is conducted through a surge absorbing element, and the low frequency alternating current is conducted through a non-polar capacitance circuit that reduces the alternating induction voltage of the embedded structure. To do.
[0018]
The invention according to claim 2 is a method of securing a buried structure, and electrically connects the buried structure and a sacrificial anode installed around the buried structure so that a corrosion-proof current flows into the buried structure. In this case, all direct current from the sacrificial anode to the buried structure through the conductor is cut off, and from the buried structure to the sacrificial anode through the conductor in accordance with a potential difference between the buried structure and the sacrificial anode. Directing direct current is conducted, and high-frequency alternating current is conducted through a surge absorbing element, and low-frequency alternating current is conducted through a non-polar capacitance circuit that reduces the AC induced voltage of the embedded structure. It is characterized by.
[0019]
The invention according to claim 3 is the above-described method for securing a buried structure, wherein the lifetime of the sacrificial anode is predicted by monitoring a direct current from the buried structure to the sacrificial anode through the conductor. Features.
[0020]
The invention according to claim 4 is the above-described buried structure security method, wherein the non-polar capacity circuit has a capacitance set so that the probe AC current density of the buried structure is within the cathodic protection control standard. It is characterized by being.
[0021]
The invention according to claim 5 is the above-described buried structure security method, wherein the non-polar capacitance circuit is composed of a plurality of capacitors, and the capacitors are connected so that the same polarities of the polar plates are opposed to each other. It is characterized by.
[0022]
The invention according to claim 6 is the above-described method for securing a buried structure, in which the conductor is cut with a continuous large current from at least the nonpolar capacitance circuit to the conductor on the buried structure side. Means is provided.
[0023]
The invention according to claim 7 is a security device for an embedded structure, and is an embedded structure comprising an electric circuit connected between the embedded structure and a low-grounded object installed around the electrolyte via an electrolyte. A surge absorbing element and a first backflow prevention element that conducts a current from the buried structure toward the low grounded object and interrupts a current in the opposite direction, connected in series, and In parallel with the surge absorbing element and the first backflow preventing element, a resistance element having a high resistance to a high frequency current and a current from the embedded structure toward the low grounded object are conducted and directed in the opposite direction. A second backflow prevention element that cuts off current is connected in series, and a nonpolar capacitance circuit that reduces the AC induced voltage of the embedded structure is connected in parallel with the second backflow prevention element. And
[0024]
The invention according to claim 8 is a security device for an embedded structure comprising an embedded circuit and an electric circuit connected between the embedded structure and a sacrificial anode installed around the embedded structure in order to allow the anticorrosion current to flow. A series of a surge absorbing element and a first backflow preventing element that conducts a current from the buried structure toward the sacrificial anode and cuts off a current that flows in the opposite direction, the surge absorbing element and the In parallel with the first backflow prevention element, a resistance element having a high resistance to a high-frequency current and a current directed from the buried structure toward the sacrificial anode and a current directed in the opposite direction are blocked. Are connected in series, and in parallel with the second backflow prevention element, a nonpolar capacitance circuit for reducing the AC induced voltage of the embedded structure is connected.
[0025]
The invention according to claim 9 is the above-described buried structure security device, which monitors a direct current from the buried structure to the sacrificial anode through the conductor in series with the second backflow prevention element. A current monitoring means is inserted.
[0026]
The invention according to claim 10 is the security device for an embedded structure described above, wherein the current monitoring means has a transmission means for transmitting a monitoring result to a remote place.
[0027]
The invention according to claim 11 is the security device for an embedded structure described above, wherein arithmetic means for predicting the life of the sacrificial anode is inserted in series with the current monitoring means based on the monitoring result of the current monitoring means. It is characterized by that.
[0028]
The invention according to claim 12 is the above-described buried structure security device, wherein the non-polar capacitance circuit is an electric device set so that a probe AC current density of the buried structure falls within a cathodic protection control standard. It is characterized by having a capacity.
[0029]
The invention according to claim 13 is the above-described buried structure security device, wherein the first or second backflow prevention element is arranged in order of a current from the buried structure toward the low grounded object or the sacrificial anode. It is characterized by comprising a directional diode.
[0030]
The invention according to claim 14 is the security device for an embedded structure described above, wherein the non-polar capacitance circuit includes a set of capacitors having different polar directions connected so that the same polarity of the polar plate polarity is opposed to each other. Two rows are provided, and capacitors having the same polarity direction are connected in parallel.
[0031]
The invention according to claim 15 is the security device for an embedded structure described above, wherein the non-polar capacitance circuit includes diodes having different directions to supply currents to capacitors in respective polar directions. To do.
[0032]
The invention according to claim 16 is the above-described buried structure security device, wherein a second surge absorbing element is connected in parallel to each capacitor.
[0033]
The invention according to claim 17 is the above-described buried structure security device, and at least connects the first surge absorbing element and the buried structure on the buried structure side from the nonpolar capacitance circuit. A conducting wire cutting means is provided in the conducting wire to cut the conducting wire with a continuous large current.
[0034]
The invention according to each claim has the following functions by having the above-described features.
[0035]
In the above-described buried structure security method and safety device, first, the buried structure and the low-grounded object or sacrificial anode installed in the vicinity of the buried structure are electrically connected to each other through a nonpolar capacitance circuit. Therefore, the AC induced voltage received by the buried structure from the high-voltage AC overhead power transmission line, AC electric railway, or the like can be quickly released from the low-grounded object or the sacrificial anode to the ground and reduced. This non-polar capacitance circuit is set so that the probe AC current density measured by the probe installed close to the buried structure is within the cathodic protection control standard. It becomes possible to prevent electric corrosion reliably.
[0036]
When a buried structure that is cathodic protected by the external power supply method is targeted, an electrolyte is interposed between the buried structure and the low-grounded object, and the space between the low-grounded object and the buried structure is between Since all direct current from the low-grounded object to the embedded structure through the conductive wire is cut off when electrically connected with the conductor, the external structure provided outside the low-grounded object is not connected to the buried structure to be cathodic protected. The anticorrosion current can be supplied from the electrode through the electrolyte, and the cathodic protection efficiency is not lowered.
[0037]
On the other hand, when a buried structure that is cathodic protected by the sacrificial anode method is targeted, all direct current from the sacrificial anode to the buried structure through the conductor is cut off, so stray current flows from the sacrificial anode. Corrosion risk due to the above can be avoided, and a direct current from the buried structure to the sacrificial anode through the conducting wire can flow with low resistance, so that a sufficient anticorrosion current can be secured.
[0038]
When a buried structure that is cathodic-proofed by the external power supply method is targeted, an electrolyte is interposed between the buried structure and the low-grounded object, and between the low-grounded object and the buried structure. Since the direct current from the buried structure to the low-grounded object is conducted according to the potential difference between the buried structure and the electrical connection with the conductor, the cathodic protection is not effective, and even if the buried structure is in a natural corrosion state, it is low. The current flowing into the buried structure through the electrolyte by the driving force caused by the negative potential around the grounded object and the plus potential around the buried structure can be reliably returned to the low grounded object via the conductor. As a result, the current flowing into the buried structure does not stray and flow out of the coating defect of the buried structure, and the progress of corrosion can be prevented even in such a natural corrosion state.
[0039]
In addition, the low frequency alternating current is made to conduct from the buried structure to the low grounded object or the sacrificial anode through the non-polar capacitance circuit, so that the low frequency alternating current induction voltage related to alternating current interference is released to the ground. On the other hand, since high-frequency alternating current is conducted through the surge absorbing element, even if lightning current containing high-frequency components flows into the buried structure, it is quickly released to the ground and buried. It is possible to avoid melting of the structure body, and it is possible to prevent the non-polar capacitance circuit for preventing AC interference from being damaged by the buffer effect of the surge absorbing element.
[0040]
In addition, the non-polar capacity circuit for preventing AC interference consists of a plurality of capacitors, and these capacitors are wired so that the same polarity of the polar plates are opposite to each other. However, it is possible to reduce the AC induced voltage by functioning other capacitors, and it is also possible to avoid short-circuiting between the buried structure and the low grounded object. Furthermore, due to the relative polarities of the polar plates of the plurality of capacitors, the current due to the discharge of the charge of the capacitors does not flow into the buried structure, and the risk of corrosion of the buried structure due to the discharge current of the capacitors can be eliminated.
[0041]
Furthermore, when a buried structure that is cathodic-protected by the sacrificial anode method is targeted, the lifetime of the sacrificial anode can be predicted by monitoring a direct current from the buried structure to the sacrificial anode through a conductor. Therefore, it is possible to easily grasp the replacement time of the sacrificial anode.
[0042]
In addition, since a conductor cutting means for cutting the conductor with a continuous large current is provided at least in the conductor on the buried structure side from the nonpolar capacitance circuit, a lightning between the buried structure and the low-grounded object or the sacrificial anode is provided. Alternatively, even when a large current due to AC induction flows, the conductive wire is disconnected after a predetermined duration, and the buried structure and the low-grounded object or the sacrificial anode are insulated. Therefore, the circuit connected between the buried structure and the low-grounded object or the sacrificial anode is protected, and for those that are cathodic protected by the external power supply method, the buried structure and the low-grounded object are electrically connected. Each circuit provided in the conducting wire connected to the terminal is not broken in conduction, and a decrease in the anticorrosion efficiency due to a short circuit between the buried structure and the low grounded object can be avoided. Also, for those that are cathodic protected by the sacrificial anode method, the cutting of the conducting wire causes an abnormality in the monitoring of the direct current from the buried structure to the sacrificial anode through the conducting wire, and the cathode is detected by detecting this anomaly. An abnormality in the anticorrosion state can be detected.
[0043]
Next, the operation of the circuit structure of the buried structure security device according to the present invention will be described as follows.
[0044]
The apparatus comprises an electric circuit connected between an embedded structure and a low-grounded object or a sacrificial anode. First, a first surge absorbing element and a first backflow prevention element are connected in series, and in parallel therewith. The high resistance element for the high frequency current and the second backflow prevention element are connected in series. Therefore, even when a large lightning voltage having a high frequency component is applied between the buried structure and the low grounded object or the sacrificial anode, the lightning current having a high frequency component is caused by the function of the high resistance element to cause the first surge. After passing through the absorption element, it is possible to escape from the low grounded object or the sacrificial anode to the ground via the first backflow prevention element. As a result, it is possible to prevent damage to the embedded structure and to protect the nonpolar capacitance circuit connected in parallel to the second backflow prevention element from high-frequency lightning current.
[0045]
Further, since the non-polar capacitance circuit has diodes having different directions to supply currents to the capacitors in the respective polar directions, only the currents in the proper directions are supplied to the capacitors in the respective polar directions. This prevents damage to the capacitor due to reverse overvoltage application.
[0046]
In addition, since the second surge absorbing element is connected in parallel to each capacitor of the non-polar capacity circuit, it is possible to prevent damage to each capacitor due to the low frequency overvoltage passing through the high resistance element. Therefore, a reduction in the effect of reducing the AC induction voltage or a short circuit between the buried structure and the low grounded object is avoided.
[0047]
Furthermore, when a buried structure that is cathodic protected by the sacrificial anode method is targeted, a current monitor that monitors the direct current from the buried structure to the sacrificial anode through the conductor in series with the second backflow prevention element. Since the means is inserted, the life of the sacrificial anode can be predicted from the monitoring result, and the replacement time of the sacrificial anode can be easily grasped. In addition, by providing a transmission means for transmitting the monitoring result of the current monitoring means to a remote place in the current monitoring means described above, it becomes possible to perform the life prediction of the sacrificial anode by a computing means in the remote place. Remote management becomes possible.
[0048]
Furthermore, the life of the sacrificial anode can be quickly grasped at the site where the safety device is installed by inserting arithmetic means for predicting the life of the sacrificial anode based on the monitoring result of the current monitor means in series with the current monitor means. Can do.
[0049]
In addition, a conductor cutting means for cutting the conductor with a continuous large current is provided in the conductor connecting the first surge absorbing element and the buried structure at least from the nonpolar capacitance circuit to the buried structure side. Even when a large current caused by lightning or AC induction flows between the buried structure and the low grounded object or the sacrificial anode, the conductor is cut after a predetermined duration, and the buried structure and the low grounded object or the sacrificial anode are Becomes insulated. Therefore, the circuit connected between the buried structure and the low-grounded object or the sacrificial anode is protected, and for those that are cathodic protected by the external power supply method, the buried structure and the low-grounded object are electrically connected. Each circuit provided in the conducting wire connected to the terminal is not broken in conduction, and a decrease in the anticorrosion efficiency due to a short circuit between the buried structure and the low grounded object can be avoided. Also, for those that are cathodic protected by the sacrificial anode method, the cutting of the conducting wire causes an abnormality in the monitoring of the direct current from the buried structure to the sacrificial anode through the conducting wire, and the cathode is detected by detecting this anomaly. An abnormality in the anticorrosion state can be detected.
[0050]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram for explaining a buried structure security method according to an embodiment of the present invention or a security system applied to the implementation of this method, and shows a buried structure that is cathodically protected by an external power supply method. The target security system is shown. In the following embodiments, the buried structure will be described as a cathode protection target pipeline, and the low grounded object disposed around the buried structure will be described as a steel casing provided when the pipeline is laid. The invention is not particularly limited to this.
[0051]
The implementation status in FIG. 1 will be described. A steel casing 2 is installed so as to cover the periphery of a pipeline 1 buried in the ground. The steel casing 2 is a bare cylindrical tube, and is installed along a section to be protected against corrosion in the pipeline 1. In the space between the steel casing 2 and the pipeline 1, an air mortar 3 that is an electrolyte is provided. Filled. Further, a terminal box 4 is formed for each set section (for example, 250 m) on the ground around the pipeline 1, and an open portion 2 </ b> A is formed in the steel casing 2 at a location corresponding to the terminal box 4. Has been.
[0052]
The pipeline 1 is a cathodic protection target conduit, and is coated with a highly electrically insulating polyethylene lining or the like. Further, in order to supply the anticorrosion current to the pipeline 1, the cathode side of the external power supply device 10 is connected via a conducting wire 10A, and the external electrode 11 connected to the anode side of the external power supply device 10 via the conducting wire 10B. Is installed in the ground around the pipeline 1. Therefore, the anticorrosion current 12 flowing out from the external electrode 11 is supplied to the pipeline 1 from the steel casing 2 through the air mortar 3, and there is a coating defect portion in the pipeline 1. In this case, an anticorrosion circuit is formed in which the anticorrosion current 12 flows into the defective portion and reaches the external power supply device 10.
[0053]
The terminal box 4 is equipped with a corrosion prevention management system for managing the cathodic protection situation. In this anticorrosion management system, a probe 20 simulating a coating defect portion is installed in a location close to the pipeline 1 in the steel casing 2, and a conducting wire 21 </ b> A conducted to the probe 20 is drawn into the terminal box 4, Therefore, the ON / OFF switch 22 and the ammeter 23 are connected in series and connected to the pipeline 1 via the conductor 21B, and the voltmeter 24 is connected in series from the probe 20 to the conductor 21A. The reference electrode (saturated copper sulfate electrode) 25 installed on the ground surface in the box 4 is connected.
[0054]
Then, when the ON / OFF switch 22 is in the ON state, the probe current I that is a measured value of the ammeter 23 and the probe ON potential that is the measured value of the voltmeter 24 or the voltmeter 24 when the switch is turned off. The anticorrosion status is managed by checking the probe OFF potential against the cathodic protection control standard. In particular, in order to evaluate the risk of AC interference, the probe current I is divided into a DC component and an AC component, the probe DC current density and the probe AC current density are obtained, and the probe inflow DC current density and the probe AC current density Whether or not the measured probe AC current density is within the reference with respect to the two-dimensional reference region with the coordinate axis as the coordinate axis is determined, thereby determining the corrosion risk.
[0055]
In such a system configuration, in the embodiment of the present invention, the pipeline security device 30 is interposed between the conductor 21 </ b> B and the conductor 21 </ b> C that electrically connect the pipeline 1 and the steel casing 2.
[0056]
The function of the pipeline security device 30 will be described. For example, a low frequency (50 Hz or 60 Hz: commercial AC frequency) received from a high-voltage AC overhead power transmission line or AC electric railway parallel to the pipeline 1. Is caused to escape from the pipeline 1 to the steel casing 2 which is a low grounded object, and the influence of the AC induction voltage of the pipeline 1 is improved within the cathodic protection control standard.
[0057]
Moreover, with respect to the direct current from the steel casing 2 which is a low grounding object to the pipeline 1 through the conductor 21B and the conductor 21C, this is interrupted in any situation to maintain the insulation state, and vice versa. The direct current from the pipeline 1 to the steel casing 2 that is a low grounded object via the conductor 21B and the conductor 21C is conducted according to the potential difference between the pipeline 1 and the steel casing 2, for example, when the potential difference becomes 400 mV. enable.
[0058]
Furthermore, even when a large lightning voltage having a high frequency component is applied between the pipeline 1 and the steel casing 2 which is a low grounded object, the high frequency alternating current is converted into the conductors 21B, 21B, 21C is made to conduct, and quickly escapes from the steel casing 2 to the ground to protect the pipeline 1 and the pipeline security device 30.
[0059]
FIG. 2 is an explanatory view showing a more specific embodiment of such a pipeline security device 30. The pipeline security device 30 is configured by an electric circuit that does not require a power source connected between a conductor 21B connected to the pipeline 1 and a conductor 21C connected to the steel casing 2 (pipeline 1 and steel The space with the casing 2 is filled with the air mortar 3 which is an electrolyte as described above.
[0060]
In this electrical circuit, a fuse 31 (conductor disconnecting means), a surge absorbing element (surge absorber) 32, and a first backflow prevention diode 33 are connected in series between the conductors 21B and 21C. In parallel with the surge absorbing element 32 and the first backflow prevention diode 33, a coil 34 which is a high resistance element with respect to a high frequency current and a second backflow prevention diode 35 are connected in series. ing. A nonpolar capacitance circuit 40 is connected in parallel with the second backflow prevention diode 35.
[0061]
The first backflow prevention diode 33 and the second backflow prevention diode 35 are installed in a forward direction with respect to a direct current directed from the pipeline 1 to the steel casing 2 which is a low grounded object, The direct current flowing from the pipeline 1 to the steel casing 2 is made conductive according to the potential difference between them (for example, operating at 400 mV), and the flow of the reverse direct current is cut off. Thus, the insulation state is maintained.
[0062]
The nonpolar capacitance circuit 40 is a circuit having an electric capacity for reducing a low-frequency AC induced voltage, and is a pipe measured as described above by the individual electric capacity of the plurality of capacitors 43, 44, 45, and 46. The electric capacity is set such that the probe AC current density of the line 1 is within the cathodic protection control standard.
[0063]
The plurality of capacitors 43, 44, 45, 46 are composed of capacitors 43, 45 having the same polarity direction and capacitors 44, 46 having opposite polar directions, and a capacitor composed of a set of the capacitor 43 and the capacitor 44. The capacitors and the capacitor rows composed of the capacitors 45 and 46 are connected so that the same polarities of the polar plates are opposed to each other. Further, capacitors having the same polarity direction (capacitor 43 and capacitor 45, capacitor 44 and capacitor 46) are connected in parallel.
[0064]
In order to supply current to the capacitors 43 and 45, a diode 42 is provided in parallel with the capacitors 44 and 46. Also, the direction of the diode 42 is such that current is supplied to the capacitors 44 and 46. A diode 41 having different characteristics is provided in parallel with the capacitors 43 and 45. Further, a surge absorbing element 47 is connected in parallel with the capacitors 43 and 45, and a surge absorbing element 48 is connected in parallel with the capacitors 44 and 46, respectively.
[0065]
The operation of each element in the pipeline security device 30 will be described.
[0066]
First, the pipeline 1 and the steel casing 2, which is a low grounded object installed around the pipeline 1, are electrically connected to each other via a nonpolar capacitance circuit 40 with respect to alternating current. Therefore, the AC induction voltage (low frequency voltage of 50 Hz or 60 Hz) received by the pipeline 1 from the surrounding high-voltage AC overhead power transmission line, AC electric railway, or the like can be reduced according to the set electric capacity of the nonpolar capacitance circuit 40. It is possible to escape from the steel casing 2 to the ground quickly. Then, this electric capacity is the probe AC current density measured by the probe 20 installed in the vicinity of the pipeline 1 and simulating the coating defect part as the electric capacity of each of the capacitors 43, 44, 45, 46. Is set so that is within the cathodic protection standard. Accordingly, it is possible to reliably prevent the risk of corrosion due to AC interference.
[0067]
In addition, in the electrical connection between the steel casing 2 and the pipeline 1 via the pipeline security device 30, the non-polar capacity circuit 40 is not all conductively damaged in the direct current from the steel casing 2 toward the pipeline 1. As long as it is blocked by the first backflow prevention diode 33 and the second backflow prevention diode 35. Therefore, the anticorrosion current can be supplied to the pipeline 1 to be cathodic protected from the external electrode 11 provided outside the steel casing 2 via the air mortar 3, and the cathodic anticorrosion efficiency for the pipeline 1 is reduced. Without making it, the steel casing 2 can be used for AC interference countermeasures.
[0068]
Further, assuming that the cathodic protection is not effective due to a failure of the external power supply device 10 and the pipeline 1 is exposed to a natural corrosion state, the periphery of the steel casing 2 is clayey soil and is on the minus side. Since the pipeline 1 covered with the air mortar 3 has a high potential (−800 mV: saturated copper sulfate electrode potential reference) and has a positive potential (−400 mV: same reference), the driving force due to this potential difference A current flows into the pipeline 1 through the air mortar 3. However, in the electrical connection between the steel casing 2 and the pipeline 1 via the pipeline security device 30, the direct current from the pipeline 1 to the steel casing 2 is a second reverse flow according to the potential difference between the two. Since it is conducted by the prevention diode 35, the flowing current can be smoothly returned to the steel casing 2. Therefore, even if there is a coating defect in the pipeline 1, the corrosion current does not leak from the coating defect, and the progress of corrosion can be stopped.
[0069]
Assuming that a large lightning voltage is applied between the pipeline 1 and the steel casing 2, the lightning current of the high frequency component is caused by the action of the coil 34 that is a high resistance element for the high frequency current. It does not flow to the second backflow prevention diode 35 and the nonpolar capacitance circuit 40 side, and after passing through the surge absorbing element 32, the first backflow prevention diode 33 causes the steel casing 2, which is a low grounded object, to move to the ground. I can escape. Therefore, not only can the pipeline 1 be prevented from being melted by lightning current, but also has an effect of protecting the nonpolar capacitance circuit 40 from lightning current of high frequency components.
[0070]
Further, even if the surge absorbing element 32 is conductively broken due to a large lightning current, the direct current flowing from the steel casing 2 to the pipeline 1 is cut off by the action of the first backflow prevention diode 33. As described above, the situation where the pipeline 1 is corroded can be avoided.
[0071]
The lightning current generally has a broadband frequency component, but the lightning current of the low frequency component is grounded from the steel casing 2 by the capacitors 43, 44, 45, and 46 of the nonpolar capacitance circuit 40 and the second backflow prevention diode 35. This can also prevent the pipeline 1 from being damaged.
[0072]
The operation of the nonpolar capacitance circuit 40 will be described. The nonpolar capacitance circuit 40 includes a plurality of capacitors 43, 44, 45, and 46. The capacitor 43 and the capacitor 44, and the capacitor 45 and the capacitor 46 each have a positive polarity. The poles are connected so that they are opposite. Therefore, the current due to the discharge of the charge of each capacitor does not flow into the pipeline 1, and the pipeline 1 is not corroded by the discharge current of each capacitor.
[0073]
Further, a combination of the diode 41 and the capacitors 44 and 46 and the diode 42 and the capacitors 43 and 45 constitutes a circuit in which an appropriate current flows through each capacitor. That is, two diodes 41 and 42 having different directions are used, and currents in appropriate directions are supplied to the capacitors having different polar directions by the respective diodes 41 and 42. According to this, a reverse voltage is not applied to each capacitor, and damage to the capacitor due to reverse overvoltage application can be avoided.
[0074]
Furthermore, since the capacitor 43 and the capacitor 44, and the capacitor 45 and the capacitor 46 are connected in series, even if one capacitor breaks down, the operation of the remaining one connected in series causes a certain amount of alternating current. If one of the capacitors in series has a function to reduce the induced voltage and is normal, the pipeline 1 and the steel casing 2 will not be short-circuited. Absent.
[0075]
Since each of the capacitors 43 to 46 is connected in parallel with the surge absorbing element 47 or 48, the capacitors 43 to 46 are prevented from being damaged by the low-frequency overvoltage that has passed through the coil 31. However, the fall of the alternating induction voltage reduction effect or the short circuit of the pipeline 1 and the steel casing 2 is avoided.
[0076]
Furthermore, a large voltage caused by lightning or AC induction is applied between the pipeline 1 and the steel casing 2, and a larger large current (for example, 10 A or more) is generated between the pipeline 1 and the steel casing 2. A fuse 31 which is a conductor cutting means is provided assuming the flow. As a result, when this large current continues for a certain period of time, the fuse 31 is blown and the pipeline 1 and the steel casing 2 are electrically insulated, so the pipeline 1 and the steel casing 2 are electrically connected. This can also prevent a decrease in the anticorrosion efficiency due to the state. When the fuse 31 is blown and the lead wire 21B is cut, a large current does not reach each downstream circuit, so that these circuits are protected, and these circuits are also broken in conduction. As a result, the pipeline 1 and the steel casing 2 do not become conductive.
[0077]
If the pulse current does not continue even if the current is large, the fuse 31 may not be blown. In this case, as described above, a large current having a high frequency component flows through the surge absorbing element 32 in an electrically conductive state, and the first backflow preventing element 33 passes through the steel casing 2 from the pipeline 1. By flowing to the ground, an impact protection measure is taken for the pipeline 1, and a large current having a low frequency component that has passed through the fuse 31 passes through the coil 34, and is caused by the second backflow prevention element 35. By flowing from the pipeline 1 to the ground through the steel casing 2 or charging the capacitors 43 to 46 of the nonpolar capacitance circuit 40, the impact protection measures for the pipeline 1 are taken.
[0078]
According to the embodiment of the present invention, since the pipeline 1 and the steel casing 2 that is a low grounded object are not short-circuited even under considerably severe conditions, there is no reduction in the cathodic protection effect. Moreover, even if the cathodic protection does not work, corrosion does not progress. And the alternating current induction voltage which concerns on alternating current interference can be reduced within the cathodic protection management standard. In addition, proper protection against lightning current is provided. When these are combined, the safety of the pipeline 1 can be reliably maintained against the influence of the surrounding environment.
[0079]
FIG. 3 is an explanatory diagram for explaining a buried structure security method according to an embodiment of the present invention or a security system applied to the implementation of this method, and a buried structure that is cathodic-protected by the sacrificial anode method. It shows a security system for. The same reference numerals are given to the same portions as those in the above-described embodiment, and a part of the overlapping description is omitted.
[0080]
The implementation status in FIG. 3 will be described. A sacrificial anode 50 (for example, an Mg electrode) is installed around the pipeline 1 buried in the ground. The sacrificial anode 50 is covered with a low grounding bag 50A in order to lower the grounding resistance. The pipeline 1 is a cathodic protection target conduit, and the pipeline 1 and the sacrificial anode 50 are electrically connected by the conducting wire 51B and the conducting wire 51C, whereby the dissimilar metal battery action between the sacrificial anode 50 and the pipeline 1 is achieved. Thus, the anticorrosion current 12 is caused to flow into the pipeline 1 from the sacrificial anode 50 through the surrounding soil.
[0081]
Further, in the terminal box 4, as in FIG. 1, an anticorrosion management system for managing the cathodic protection status is provided. In this anticorrosion management system, a probe 20 simulating a coating defect portion is installed at a location close to the pipeline 1, and a conducting wire 51 </ b> A conducted to the probe 20 is drawn into the terminal box 4, where the ON / OFF switch 22 is provided. And an ammeter 23 are connected in series and connected to the pipeline 1 via a conductor 51B, and a voltmeter 24 is connected in series from the probe 20 to the conductor 51A, and this is connected to the ground surface in the terminal box 4 Is connected to a reference electrode (saturated copper sulfate electrode) 25.
[0082]
Then, when the ON / OFF switch 22 is in the ON state, the probe current I that is a measured value of the ammeter 23 and the probe ON potential that is the measured value of the voltmeter 24 or the voltmeter 24 when the switch is turned off. The anticorrosion status is managed by checking the probe OFF potential against the cathodic anticorrosion management standard, as in the embodiment of FIG.
[0083]
In such a system configuration, in the embodiment shown in FIG. 3, the pipeline security device 60 is interposed between the conductor 51B and the conductor 51C that electrically connect the pipeline 1 and the sacrificial anode 50.
[0084]
The function of the pipeline security device 60 will be described. The outline is the same as that of the pipeline security device 30 according to the above-described embodiment. For example, the high-voltage AC overhead power transmission line parallel to the pipeline 1 is used. Alternatively, a low frequency (50 Hz or 60 Hz: commercial AC frequency) AC induced voltage received from an AC electric railway or the like is released from the pipeline 1 to the sacrificial anode 50 that also serves as a ground electrode, and the AC induced voltage of the pipeline 1 This is to improve the impact of the above within the cathodic protection standards.
[0085]
Further, with respect to the direct current from the sacrificial anode 50 to the pipeline 1 through the conductor 51B and the conductor 51C, the stray current flowing into the pipeline 1 from the sacrificial anode 50 is blocked by blocking this, and vice versa. A direct current flowing from the pipeline 1 to the sacrificial anode 50 through the 51B and the conductive wire 51C flows with a low resistance in accordance with the potential difference between the pipeline 1 and the sacrificial anode 50, and the anticorrosion current sufficient for cathodic protection by the sacrificial anode method. It is always done by the occurrence of.
[0086]
Further, even when a large lightning voltage having a high frequency component is applied between the pipeline 1 and the sacrificial anode 50, the high frequency alternating current causes the conductors 51B and 51C to conduct through the surge function and quickly. The pipeline 1 and the pipeline security device 60 are protected from the sacrificial anode 50 to the ground.
[0087]
FIG. 4 is an explanatory view showing a more specific embodiment of such a pipeline security device 60. Most of the elements are the same as those in the pipeline security device 30 described above, and common elements are denoted by the same reference numerals, and a duplicate description is partially omitted. Here, the pipeline-side terminal 60A in the pipeline security device 60 is connected to the conducting wire 51B in FIG. 3, and the sacrificial anode-side terminal 60B is connected to the conducting wire 51C in FIG. As an additional element, a current monitor circuit 61 for monitoring the direct current from the pipeline 1 to the sacrificial anode 50 through the conductors 51B and 51C is inserted in series with the second backflow prevention diode 35, and further, An arithmetic circuit 62 for predicting the life of the sacrificial anode 50 based on the monitoring result of the current monitor circuit 61 is inserted. In addition, the current monitor circuit 61 incorporates a transmission circuit that transmits the monitoring result to a remote place as necessary.
[0088]
In such an electric circuit, the first backflow prevention diode 33 and the second backflow prevention diode 35 are installed in the forward direction with respect to the direct current from the pipeline 1 to the sacrificial anode 50. Thus, the direct current from the pipeline 1 to the sacrificial anode 50 is made conductive according to the potential difference between the two to promote the generation of an effective anticorrosion current, and the flow of the reverse direct current is interrupted. Thus, the stray current is prevented from flowing into the pipeline 1 from the sacrificial anode 50. The functions and operations of the surge absorbing element 32, the coil 34, and the nonpolar capacitance circuit 40 are as described above.
[0089]
According to this, the pipeline 1 and the sacrificial anode 50 installed around the pipeline 1 are electrically connected via the nonpolar capacitance circuit 40 with respect to the alternating current. Therefore, the AC induction voltage (low frequency voltage of 50 Hz or 60 Hz) received by the pipeline 1 from the surrounding high-voltage AC overhead power transmission line, AC electric railway, or the like can be reduced according to the set electric capacity of the nonpolar capacitance circuit 40. A part of it can be quickly released from the sacrificial anode 50 to the ground. Then, this electric capacity is the probe AC current density measured by the probe 20 installed in the vicinity of the pipeline 1 and simulating the coating defect part as the electric capacity of each of the capacitors 43, 44, 45, 46. Is set so that is within the cathodic protection standard. Accordingly, it is possible to reliably prevent the risk of corrosion due to AC interference.
[0090]
Further, in the electrical connection between the sacrificial anode 50 and the pipeline 1 via the pipeline security device 60, the direct current from the sacrificial anode 50 to the pipeline 1 is not electrically connected to the nonpolar capacitance circuit 40. All are blocked by the first backflow prevention diode 33 and the second backflow prevention diode 35. Therefore, it is possible to reliably avoid the occurrence of corrosion risk due to inflow of stray current.
[0091]
Further, assuming a case where a large lightning voltage is applied between the pipeline 1 and the sacrificial anode 50, the lightning current of the high frequency component is caused by the action of the coil 34 serving as a high resistance element with respect to the high frequency current. The second backflow prevention diode 35 and the non-polar capacitance circuit 40 do not flow, and after passing through the surge absorbing element 32, the first backflow prevention diode 33 can escape from the sacrificial anode 50 to the ground. Therefore, not only can the pipeline 1 be prevented from being melted by lightning current, but also has an effect of protecting the nonpolar capacitance circuit 40 from lightning current of high frequency components.
[0092]
And, by such an action, the risk that the pipeline security device 60 installed between the pipeline 1 and the sacrificial anode 50 will be continually broken down or dielectrically broken down considerably, so that the sacrificial anode always operates normally. Thus, it becomes possible to generate an anticorrosive current from the sacrificial anode 50 to the pipeline 1 through the soil, and the cathodic anticorrosion for the pipeline 1 can be reliably performed.
[0093]
Further, the pipeline security device 60 can obtain a more effective action by adding the above-described additional elements.
[0094]
In other words, as described above, if the sacrificial anode 50 is operating normally, the generated anticorrosion current decreases with time. In the normal operation, the electric capacity and generated electricity of the installed sacrificial anode 50 are reduced. The lifetime of the sacrificial anode 50 can be predicted by the amount. In order to obtain this generated amount of electricity, the pipeline security device 60 receives a direct current from the pipeline 1 to the sacrificial anode 50 through the conductors 51B and 51C in series with the second backflow prevention diode 35 as described above. A current monitor circuit 61 to be monitored is inserted. In addition, an arithmetic circuit 62 for predicting the life of the sacrificial anode 50 based on the monitoring result of the current monitor circuit 61 is inserted.
[0095]
According to this, the remaining life of the sacrificial anode 50 can be grasped at the site where the sacrificial anode 50 is installed, for example, by displaying the output of the arithmetic circuit on the display device. Further, by incorporating a transmission circuit into the current monitor circuit 61 and sending the monitoring result to a remote place, the life calculation of the sacrificial anode 50 can be performed by remote processing means, and the sacrificial anode 50 can be remotely managed. .
[0096]
In addition, the monitoring of the generated anticorrosion current by the current monitor circuit 61 can grasp not only the life of the sacrificial anode 50 but also the abnormal state of the pipeline security device 60, so comprehensive sacrificial anode 50 management is performed on site. Or it can be easily performed in a remote place.
[0097]
Furthermore, when a large voltage due to lightning or AC induction is applied between the pipeline 1 and the sacrificial anode 50, a larger current (for example, 10 A or more) flows between the pipeline 1 and the sacrificial anode 50. Is provided with a fuse 31 which is a conductor cutting means. As a result, when this large current flows for a certain period of time, the fuse 31 is blown, and the large current does not reach the circuits on the downstream side, so that these circuits can be protected. In addition, the disconnection of the conducting wire causes an abnormality in the monitoring of the direct current from the pipeline 1 to the sacrificial anode 50 through the conducting wire. By detecting this abnormality, it is possible to detect an abnormality in the cathodic protection state.
[0098]
【Example】
The specific Example of this invention is shown. In the implementation situation shown in FIG. 1, the pipeline security device 30 shown in FIG. 3 was used, the coil 34 was set to 200 μH, and the electric capacities of the capacitors 43 to 46 were each set to 22000 μF.
[0099]
5 and 6 are explanatory diagrams showing the results of the implementation. FIGS. 5A and 5B show time-dependent changes in ground potential (saturated copper sulfate electrode potential reference) and probe current density of <probe 20 + pipeline 1> before installation of the pipeline security device 30. FIG. (C) and (d) in FIG. 6 show the time-dependent changes in the ground potential and probe current density of <probe 20 + pipeline 1> after installation of the pipeline security device 30, respectively. (Where time on the horizontal axis is T ₀ At the time of (1. 10 sec), the ON / OFF switch 22 of the system shown in FIG. 1 is turned OFF to cut off the connection between the probe 20 and the pipeline 1. ). The ground potential and current density shown in FIGS. 5A to 5D both have a data sampling time interval of 0.1 ms. The current density is positive in the probe inflow direction. As is clear from this result, the amplitude of the ground potential of <Probe 20 + Pipeline 1> is reduced to about 1 / 2.5 and the amplitude of the probe current density is reduced to about 1/30. It is possible.
[0100]
FIG. 6 shows the effect of the AC interference countermeasure, and the probe inflow DC current density I _DC And probe AC current density I _AC The anticorrosive effect with respect to the cathodic anticorrosion management standard in the coordinates represented by is shown. The range indicated by the black frame indicates the cathodic protection management standard (see Yuji Hosokawa, Fumio Hatakeyama, Yasuhiro Nakamura: Materials and Environment, Vol. 51, No. 5 (2002)). According to this, the probe current density I before installing the pipeline security device 30 is ₁ (I _1DC , I _1AC However, after the pipeline security device 30 is installed, the probe current density I ₂ (I _2DC , I _2AC It can be confirmed that it is within the cathodic protection standards. As described above, the feature of the present invention is that the anticorrosion effect is always evaluated by comparison with the cathodic anticorrosion management standard, and an apparatus suitable for the evaluation is set.
[0101]
【The invention's effect】
Since the present invention is configured as described above, it is possible to take measures against AC interference while maintaining an effective cathodic protection state regardless of the sacrificial anode method or the external power supply method, and it is lightning in a wide frequency band including a high frequency component. It is possible to provide a security method and a security device for an embedded structure that can cope with impact protection against current.
[0102]
In addition, for buried structures that are cathodic-protected by the sacrificial anode method, the corrosion risk due to stray currents can be avoided, and at the same time, sufficient functions can be obtained as a countermeasure against AC interference. For buried structures, it is possible to reduce the AC induced voltage using this low grounded object without short-circuiting the buried structure and the low grounded object provided around it, and cathodic protection It does not induce electrical corrosion in buried structures even under natural corrosion conditions that do not work.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram for explaining a buried structure security method according to an embodiment of the present invention or a security system (targeting an external power supply method) applied to the implementation of this method.
FIG. 2 is an explanatory view showing a more specific embodiment of the pipeline security device of the present invention.
FIG. 3 is an explanatory view for explaining a buried structure security method according to another embodiment of the present invention or a security system (targeting a sacrificial anode method) applied to the implementation of this method.
FIG. 4 is an explanatory view showing a more specific embodiment of the pipeline security device of the present invention.
FIG. 5 is an explanatory diagram showing an implementation effect in the embodiment of the present invention.
[Fig. 6]
It is explanatory drawing which shows the implementation effect in the Example of this invention.
[Explanation of symbols]
1 Pipeline (buried structure)
2 Steel casing (low grounding)
3 Air mortar (electrolyte)
4 Terminal box
10 External power supply
10A, 10B conductor
11 External electrode
12 Anticorrosion current
20 probes
21A, 21B, 21C, 51A, 51B, 51C
22 ON / OFF switch
23 Ammeter
24 Voltmeter
25 Reference electrode (saturated copper sulfate electrode)
30, 60 Pipeline security device
31 Fuse (conductor cutting means)
32 Surge absorber (first surge absorber)
33 First backflow prevention diode (first backflow prevention element)
34 Coil (resistance element)
35 Second backflow prevention diode (second backflow prevention element)
40 Nonpolar capacitance circuit
41, 42 Diode
43-46 capacitors
47, 48 Surge absorber (second surge absorber)
50 Sacrificial anode
61 Current monitor circuit
62 Arithmetic circuit

Claims (17)

When electrically connecting a buried structure and a low-grounded object installed around it via an electrolyte with a conducting wire,
All direct currents directed from the low grounding object to the embedded structure through the conductor are cut off, and from the embedded structure to the low grounded object through the conductor in accordance with a potential difference between the embedded structure and the low grounded object. Directing the direct current to go,
A buried structure characterized in that high-frequency alternating current is conducted through a surge absorbing element, and low-frequency alternating current is conducted through a nonpolar capacitance circuit that reduces the alternating current induction voltage of the buried structure. Security method. When electrically connecting the buried structure and a sacrificial anode installed around the buried structure so as to allow an anticorrosion current to flow into the buried structure by a conducting wire,
All direct currents from the sacrificial anode to the buried structure through the conductor are cut off, and a direct current from the buried structure to the sacrificial anode through the conductor in accordance with a potential difference between the buried structure and the sacrificial anode. Continuity,
A buried structure characterized in that high-frequency alternating current is conducted through a surge absorbing element, and low-frequency alternating current is conducted through a nonpolar capacitance circuit that reduces the alternating current induction voltage of the buried structure. Security method. The method for securing a buried structure according to claim 2, wherein the life of the sacrificial anode is predicted by monitoring a direct current from the buried structure to the sacrificial anode through the conductive wire. The embedded capacity according to claim 1, wherein the non-polar capacity circuit has an electric capacity set so that a probe AC current density of the embedded structure falls within a cathodic protection control standard. How to secure the structure. 5. The embedded structure according to claim 1, wherein the nonpolar capacitance circuit includes a plurality of capacitors, and the capacitors are connected so that the same polarities of the polar plates are opposed to each other. Security method. The buried structure according to claim 1, further comprising: a conductor cutting means for cutting the conductor with a continuous large current in the conductor on the buried structure side from at least the nonpolar capacitance circuit. How to secure things. A safety device for an embedded structure comprising an electric circuit connected between the embedded structure and a low grounded object installed around the electrolyte via an electrolyte,
A first surge absorbing element and a first backflow prevention element that conducts a current from the buried structure toward the low grounded object and blocks a current in the opposite direction are connected in series.
In parallel with the surge absorbing element and the first backflow preventing element, a resistance element having a high resistance to a high frequency current and a current from the embedded structure toward the low grounded object are conducted and in the opposite direction. A second backflow prevention element that cuts off the current that flows is connected in series,
A buried structure security device, wherein a non-polar capacity circuit for reducing an AC induced voltage of the buried structure is connected in parallel with the second backflow prevention element. A buried structure security device comprising an electrical circuit connected between a buried structure and a sacrificial anode installed around the buried structure in order to allow an anticorrosive current to flow into the buried structure,
A first surge absorbing element and a first backflow preventing element that conducts a current from the buried structure toward the sacrificial anode and cuts off a current in the opposite direction are connected in series.
In parallel with the surge absorbing element and the first backflow preventing element, a resistance element having a high resistance to a high-frequency current and a current from the embedded structure toward the sacrificial anode are conducted and directed in the opposite direction. A second backflow prevention element that cuts off the current is connected in series,
A buried structure security device, wherein a non-polar capacity circuit for reducing an AC induced voltage of the buried structure is connected in parallel with the second backflow prevention element. 9. The embedded structure according to claim 8, wherein current monitoring means for monitoring a direct current from the embedded structure toward the sacrificial anode through the conducting wire is inserted in series with the second backflow prevention element. Object security device. 10. The buried structure security apparatus according to claim 9, wherein the current monitoring means includes transmission means for transmitting a monitoring result to a remote place. 11. The security device for an embedded structure according to claim 9 or 10, wherein arithmetic means for predicting a life of the sacrificial anode is inserted in series with the current monitoring means based on a monitoring result of the current monitoring means. . The non-polar capacity circuit includes an electric capacity set so that a probe AC current density of the embedded structure is within a cathodic protection control standard. Security device for buried structures. The said 1st or 2nd backflow prevention element consists of a diode of a forward direction with respect to the electric current which goes to the said low earthing | grounding thing or the said sacrificial anode from the said embedded structure. Equipment for buried structures. The non-polar capacitance circuit is provided with two rows of a pair of capacitors having different polar directions connected so that the same polarity of the polar plates of the electrodes are opposite to each other, and the capacitors having the same polarity direction are connected in parallel. The embedded structure security device according to any one of claims 7 to 13. The embedded structure security device according to any one of claims 7 to 14, wherein the non-polar capacitance circuit includes diodes having different directions to supply currents to capacitors in respective polar directions. The buried structure security device according to claim 14 or 15, wherein a second surge absorbing element is connected in parallel to each capacitor. Conductive wire cutting means for cutting the conductive wire with a continuous large current is provided at least in the conductive wire connecting the first surge absorbing element and the embedded structure on the embedded structure side from the nonpolar capacitance circuit. The buried structure security device according to any one of claims 7 to 16.

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