Flexible anode and pipeline lap joint point on-site troubleshooting method

Abstract

The invention provides an on-site troubleshooting method for a lap joint point of a flexible anode and a pipeline. The on-site troubleshooting method comprises the following steps: closing a flexible anode impressed current cathodic protection system, carrying out a pipeline-to-ground potential distribution test, picking out an area with relatively positive pipe-to-ground natural potential, and carrying out local excavation; after the flexible anode body is excavated, a local disconnection test is carried out, changes of potential to ground of the anode body on the two sides of a disconnection part before and after disconnection are measured, according to the distribution position of the most negative potential to ground of the potential of the anode body, the part of the lap joint of the flexible anode and the pipeline is checked, the part is excavated, and the lap joint is disconnected. Therefore, the lap joint fault of the flexible anode and the pipeline is eliminated, and the cathode protection system is recovered to be normal. Compared with a traditional method for overall excavation troubleshooting or complete replacement of new anodes when the flexible anodes fail, the troubleshooting method has the advantages that large-area excavation operation is avoided, and the engineering difficulty and the construction cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of cathodic protection, and in particular to an on-site inspection method for overlapping points between a flexible anode and a pipeline. Background Art

[0002] Flexible anode is a type of impressed current cathodic protection auxiliary anode ground bed. The flexible anode is connected to the positive pole of the power supply. The current flows from the positive pole of the power supply along the cable to the flexible anode, and then flows from the flexible anode through the soil into the pipeline, thereby providing cathodic protection for the buried pipeline. Flexible anodes are generally laid parallel to the protected pipeline, so they have the characteristics of uniform distribution of protection potential and little interference to the outside world. They are widely used in regional cathodic protection of oil and gas stations, especially newly built oil and gas stations. There are two types of flexible anodes. The first generation of flexible anodes are conductive polymer flexible anodes produced by Raychem, USA, but the anode body was burned due to local current density concentration during application. Later, the second generation of flexible anodes with mixed metal oxides as anode core materials came out and replaced the first generation of anodes. Since the flexible anode is laid close to the protected pipeline in actual application, the flexible anode body may overlap with the pipeline due to irregular operation, unreasonable laying method or ground subsidence, resulting in abnormal pipeline potential to the ground, which seriously affects the effect of cathodic protection. It is difficult to conduct on-site inspection of the local overlap between the flexible anode and the buried pipeline. How to effectively inspect and handle the overlap has become a technical problem that affects the cathodic protection effect of the flexible anode and restricts the application of the flexible anode in actual production. Summary of the invention

[0003] The present invention aims to provide a method and device for on-site inspection of the flexible anode and pipeline overlap points, which can overcome the above problems or at least partially solve the above problems.

[0004] To achieve the above object, the technical solution of the present invention is specifically implemented as follows:

[0005] The present invention provides a method for on-site inspection of a flexible anode and a pipeline joint, comprising:

[0006] Turn off the flexible anode impressed current cathodic protection power supply device;

[0007] Determine appropriate test points based on pipeline and flexible anode distribution;

[0008] Measuring the potential of the buried pipeline to the ground at the test point to obtain pipeline-to-ground potential test data;

[0009] According to the distribution of pipelines and flexible anodes, combined with the pipeline-to-ground potential test data, select areas where the pipeline-to-ground potential meets the preset rules for local excavation until the flexible anode body is exposed;

[0010] Measure the ground potential of both sides of the flexible anode to obtain the ground potential test data before both sides of the flexible anode are disconnected;

[0011] Determine the local disconnection position of the flexible anode, disconnect the flexible anode, measure the ground potential of both sides of the flexible anode, and obtain the ground potential test data after both sides of the flexible anode are disconnected;

[0012] Determine the side with abnormal potential change according to the positive and negative potential changes in the ground potential test data before the two sides of the flexible anode are disconnected and the ground potential test data after the two sides of the flexible anode are disconnected;

[0013] Excavation is carried out along the pipeline on the side where the potential changes abnormally, and the distribution of the flexible anode potential to the ground is tested. The overlapping point is determined based on the negative deviation trend of the flexible anode potential to the ground.

[0014] Optionally, the method further comprises: disconnecting the overlapping point to eliminate the overlapping fault between the flexible anode and the pipeline.

[0015] Optionally, the method further comprises: confirming the treatment effect by a potential test.

[0016] Optionally, measuring the potential of the buried pipeline to the ground at the test point to obtain pipeline-to-ground potential test data includes:

[0017] Lead out a wire from the ground metal structure that is electrically connected to the underground pipeline and connect it to the red probe of the multimeter;

[0018] Connect one end of another long wire to the black test lead of a multimeter, and connect the other end of the other wire to a temporary reference electrode, wherein the temporary reference electrode is a copper / copper sulfate reference electrode, and place the copper / copper sulfate reference electrode on the moist soil directly above the pipeline;

[0019] The multimeter is adjusted to the DC voltage position, and the value of the multimeter is recorded as pipeline-to-ground potential test data.

[0020] Optionally, the step of selecting a pipeline to perform local excavation on an area where the ground potential meets a preset rule includes:

[0021] The corresponding test points of the measured pipeline-to-ground potential are analyzed, and the area with relatively positive pipeline-to-ground potential is selected. Local excavation is carried out along the pipeline and anode according to the construction drawings during the construction of the cathodic protection system. The excavation size ensures that personnel can enter to perform measurements and disconnect operations, and the excavation depth is to expose the pipeline and flexible anode body.

[0022] Optionally, measuring the ground potential of both sides of the flexible anode to obtain ground potential test data before both sides of the flexible anode are disconnected includes:

[0023] Lead a wire from the flexible anode body in the excavation pit to the red probe of the multimeter;

[0024] Connect one end of another long wire to the black test lead of a multimeter, and connect the other end of the other long wire to a temporary reference electrode, wherein the temporary reference electrode is a copper / copper sulfate reference electrode, and place the copper / copper sulfate reference electrode on moist soil near the anode;

[0025] Adjust the multimeter to the DC voltage position, and record the value of the multimeter as the ground potential test data before the two sides of the flexible anode are disconnected;

[0026] The measuring of the ground potential of both sides of the flexible anode to obtain the ground potential test data after both sides of the flexible anode are disconnected includes:

[0027] Lead a wire from the flexible anode body to the red probe of the multimeter;

[0028] Connect one end of another long wire to the black test lead of a multimeter, and connect the other end of the other long wire to a temporary reference electrode, wherein the temporary reference electrode is a copper / copper sulfate reference electrode, and place the copper / copper sulfate reference electrode on moist soil near the anode;

[0029] Adjust the multimeter to the DC voltage position, and record the value of the multimeter as the ground potential test data after the two sides of the flexible anode are disconnected;

[0030] Optionally, the error of the copper sulfate reference electrode does not exceed ±5mV.

[0031] Optionally, the method further comprises: testing the self-corrosion potential;

[0032] The test of self-corrosion potential includes:

[0033] The multimeter is used to test the pipeline potential. The multimeter has a filtering function and its internal impedance is not less than 10MΩ.

[0034] Optionally, the area that complies with the preset rule is: an area with a relatively positive potential, and the relatively positive potential is compared with the normal potential of this type of material in general soil.

[0035] Optionally, the material of the pipeline is carbon steel material, and the flexible anode is a mixed metal oxide flexible anode.

[0036] It can be seen that the on-site inspection method and device of the flexible anode and pipeline overlap points provided by the present invention solves the problem of difficulty in determining the overlap point position when the regional flexible anode cathodic protection system is overlapped with the pipeline during service, extends the service life of the cathodic protection system, solves the problem that oil and gas stations could only be excavated as a whole and replaced with new anodes, and reduces the maintenance cost of flexible anode cathodic protection systems in oil and gas stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0038] Figure 1 A flow chart of a method for on-site inspection of a flexible anode and a pipeline joint provided by an embodiment of the present invention;

[0039] Figure 2 A flowchart of a specific method for on-site inspection of the flexible anode and pipeline joint points provided by an embodiment of the present invention;

[0040] Figure 3 A schematic diagram of test point distribution provided by an embodiment of the present invention;

[0041] Figure 4 A schematic diagram of pipeline-to-ground potential test results before joint point inspection and treatment provided in an embodiment of the present invention;

[0042] Figure 5 A schematic diagram of cutting off the 2# anode T-joint provided in an embodiment of the present invention;

[0043] Figure 6 A schematic diagram of anode-to-ground potential test results after the 1# and 2# anodes are disconnected according to an embodiment of the present invention;

[0044] Figure 7 A schematic diagram of the potential of anode 1# to ground and the position of the measuring point provided in an embodiment of the present invention;

[0045] Figure 8 A schematic diagram of pipeline-to-ground potential test results before and after the overlap point inspection and processing provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0047] The core of the present invention is: first, turn off the flexible anode impressed current cathodic protection system, conduct a test on the distribution of pipeline-to-ground potential, select the area with a relatively positive natural potential between the pipe and the ground, and conduct local excavation; after digging the flexible anode body, conduct a local disconnection test, measure the change of the anode body-to-ground potential on both sides of the disconnection part before and after disconnection, the area where the anode body potential is positively offset to the ground is far away from the overlap position, and the area where the anode body potential is negatively offset is close to the overlap position, according to the distribution position of the most negative anode body potential to the ground, find out the location of the flexible anode and pipeline overlap point, excavate the location, disconnect the overlap point, thereby eliminating the flexible anode and pipeline overlap fault, and restore the cathodic protection system to normal. Compared with the traditional method of using overall excavation to check or replace all new anodes when the flexible anode fails, this troubleshooting method avoids large-scale excavation operations and reduces engineering difficulty and construction costs.

[0048] Figure 1 A flow chart showing a method for checking the on-site connection between a flexible anode and a pipeline provided by an embodiment of the present invention is shown. Figure 1 The on-site inspection method of the flexible anode and pipeline joint point provided by the embodiment of the present invention includes:

[0049] S1, turn off the flexible anode impressed current cathodic protection power supply device.

[0050] Specifically, the present invention first turns off the flexible anode impressed current cathodic protection power supply device, so that no power impressed current flows between the flexible anode and the pipeline, ensuring that the subsequent measured potential is the ground potential after the pipeline and the anode are overlapped. The material of the pipeline of the present invention is carbon steel material, and the flexible anode is a mixed metal oxide flexible anode.

[0051] S2, determine the appropriate test points based on the pipeline and flexible anode distribution.

[0052] Specifically, the present invention selects appropriate test points according to the distribution of pipelines and flexible anodes, ensures that the test points cover the abnormal cathodic protection potential area, the field conditions of the test points meet the potential test requirements, and the test points are distributed as evenly as possible.

[0053] S3, measuring the potential of the buried pipeline to the ground at the test point to obtain pipeline-to-ground potential test data.

[0054] Specifically, the present invention measures the potential of the buried pipeline to the ground at the point to be detected.

[0055] As an optional implementation of an embodiment of the present invention, measuring the potential of the buried pipeline to the ground at the test point and obtaining the pipeline to ground potential test data includes: leading a wire from a ground metal structure electrically connected to the underground pipeline and connecting it to the red test lead of a multimeter; connecting one end of another long wire to the black test lead of the multimeter, and connecting the other end of the other wire to a temporary reference electrode, wherein the temporary reference electrode is a copper / copper sulfate reference electrode, and placing the copper / copper sulfate reference electrode on the moist soil directly above the pipeline; adjusting the multimeter to the DC voltage position, and recording the value of the multimeter as the pipeline to ground potential test data. Wherein, the error of the copper sulfate reference electrode does not exceed ±5mV.

[0056] S4, according to the distribution of pipelines and flexible anodes, combined with the pipeline-to-ground potential test data, select areas where the pipeline-to-ground potential meets the preset rules for local excavation until the flexible anode body is exposed.

[0057] As an optional implementation of the embodiment of the present invention, the area that meets the preset rules is: an area with a relatively positive potential, and the relatively positive potential is compared with the normal potential of the material in general soil.

[0058] Specifically, according to the distribution of pipelines and flexible anodes and combined with the pipeline-to-ground potential test data, areas with relatively positive pipeline-to-ground potential are selected for local excavation until the flexible anode body is exposed.

[0059] As an optional implementation manner of an embodiment of the present invention, selecting an area where the pipeline-to-ground potential meets preset rules for local excavation includes: analyzing the measured pipeline-to-ground potential corresponding to the test points, selecting an area where the pipeline-to-ground potential is relatively positive, and performing local excavation along the pipeline and the anode according to the construction drawings when the cathodic protection system is constructed. The excavation size ensures that personnel can enter therein to perform measurement and disconnection operations, and the excavation depth is to expose the pipeline and the flexible anode body.

[0060] S5, measuring the ground potential of both sides of the flexible anode to obtain the ground potential test data before both sides of the flexible anode are disconnected;

[0061] S6, determining the local disconnection position of the flexible anode, disconnecting the flexible anode, measuring the ground potential of both sides of the flexible anode, and obtaining ground potential test data after both sides of the flexible anode are disconnected;

[0062] S7, determining the side with abnormal potential change according to the positive and negative potential changes in the ground potential test data before the two sides of the flexible anode are disconnected and the ground potential test data after the two sides of the flexible anode are disconnected.

[0063] Specifically, the present invention determines the disconnection position, measures the ground potential of the anodes on both sides of the disconnection point before disconnection, partially disconnects the flexible anode body exposed by excavation, and then measures the ground potential of the anodes on both sides of the disconnection point again, and finds the side with abnormal potential change according to the positive and negative changes in potential.

[0064] As an optional implementation of an embodiment of the present invention, measuring the ground potential of both sides of the flexible anode to obtain the ground potential test data of both sides of the flexible anode before disconnection includes: leading a wire from the flexible anode body in the excavation pit and connecting it to the red test lead of a multimeter; taking one end of another long wire and connecting it to the black test lead of the multimeter, and connecting the other end of the other long wire to a temporary reference electrode, wherein the temporary reference electrode selects a copper / copper sulfate reference electrode, and the copper / copper sulfate reference electrode is placed on the moist soil near the anode; adjusting the multimeter to the DC voltage position, and recording the value of the multimeter as the ground potential test data before both sides of the flexible anode are disconnected;

[0065] Measuring the ground potential of both sides of the flexible anode to obtain the ground potential test data after the two sides of the flexible anode are disconnected includes: leading a wire from the flexible anode body and connecting it to the red test lead of the multimeter; taking one end of another long wire and connecting it to the black test lead of the multimeter, and connecting the other end of the other long wire to a temporary reference electrode, wherein the temporary reference electrode selects a copper / copper sulfate reference electrode, and the copper / copper sulfate reference electrode is placed on moist soil near the anode; adjusting the multimeter to the DC voltage position, and recording the value of the multimeter as the ground potential test data after the two sides of the flexible anode are disconnected.

[0066] Specifically, the ground potential test of the flexible anode of the present invention is as follows: a wire is drawn from the flexible anode body in the excavation pit and connected to the red test lead of the multimeter, another long wire is taken and connected to the black test lead of the multimeter, and the other end of the wire is connected to a temporary reference electrode. The temporary reference electrode selects a copper / copper sulfate reference electrode, and the copper / copper sulfate reference electrode is placed on the moist soil near the anode. Adjust the multimeter to the DC voltage gear, and record its value as the ground potential of the measured flexible anode. Among them, the error of the copper sulfate reference electrode does not exceed ±5mV.

[0067] S8, excavate along the pipeline on the side with abnormal potential change, test the distribution of flexible anode potential to the ground, and determine the overlap point based on the negative deviation trend of the flexible anode potential to the ground.

[0068] Specifically, at the point where the flexible anode and the pipeline overlap, the ground potential of the pipeline is more positive than that of other positions, and the ground potential of the flexible anode is more negative than that of other positions. Before disconnection, measure the ground potential of the anode and pipeline on both sides of the disconnection point. After partially disconnecting the flexible anode, measure the ground potential of the anode and pipeline on both sides of the disconnection point again. Compare the changes in the ground potential of the flexible anode before and after disconnection. If the ground potential of the flexible anode is negatively offset, the overlap point is on the anode body on that side, otherwise it is the opposite.

[0069] As an optional implementation of the embodiment of the present invention, the on-site inspection method of the flexible anode and pipeline overlap point provided by the embodiment of the present invention also includes: S9, disconnecting the overlap point to eliminate the overlap fault between the flexible anode and the pipeline.

[0070] As an optional implementation of the embodiment of the present invention, the on-site inspection method of the flexible anode and pipeline joint provided by the embodiment of the present invention further includes: S10, confirming the treatment effect through potential testing.

[0071] Specifically, the present invention excavates along the pipeline on the side where the potential changes abnormally, tests the potential distribution of the flexible anode to the ground, finds out the overlap point based on the negative deviation trend of the potential of the flexible anode to the ground, disconnects the overlap point, and confirms the treatment effect through potential testing.

[0072] As an optional implementation manner of an embodiment of the present invention, the on-site inspection method of the flexible anode and pipeline overlap point provided by the embodiment of the present invention also includes: Also includes: S12, testing the self-corrosion potential; wherein, testing the self-corrosion potential includes: using a multimeter to test the pipeline potential, the multimeter has a filtering function, and its internal impedance is not less than 10MΩ.

[0073] It can be seen that the on-site inspection method of the flexible anode and pipeline overlap points provided by the embodiment of the present invention solves the problem of difficulty in determining the overlap point position when the regional flexible anode cathodic protection system is overlapped with the pipeline during service, extends the service life of the cathodic protection system, solves the problem that oil and gas stations could only be excavated as a whole and replaced with new anodes, and reduces the maintenance cost of flexible anode cathodic protection systems in oil and gas stations.

[0074] It can be seen that the present invention has the following beneficial effects:

[0075] Beneficial technical effects of the present invention:

[0076] (1) By combining local excavation and disconnection test, the overlap position of the flexible anode and the pipeline can be accurately determined, avoiding large-scale blind excavation and unnecessary damage.

[0077] (2) By accurately locating and effectively handling the overlap points, interference and damage to the entire cathodic protection system are reduced, and the maintenance and repair costs of the system are reduced.

[0078] (3) After the overlap point is treated, the normal operation of the cathodic protection system can be quickly restored, and the treatment effect can be confirmed through potential testing, which greatly shortens the system downtime.

[0079] (4) This method is not only suitable for checking the overlap between flexible anodes and pipelines, but can also be extended to other similar cathodic protection system fault troubleshooting and treatment, and has strong applicability and universality.

[0080] The following, combined Figures 2 to 8 , a specific example of the on-site inspection method of the flexible anode and pipeline joint provided by the embodiment of the present invention is described:

[0081] Prepare test instruments and related materials, conduct field investigations at the test site, confirm that the constant potential instrument is turned off, determine the potential test point, conduct self-corrosion potential test on buried pipelines, determine the local excavation point, conduct self-corrosion potential test on flexible anodes, disconnect the anodes, and determine the specific location of the lap joint. Figure 2 shown.

[0082] At an oil and gas station, the cathodic protection effect of the valve group area has been difficult to meet the -850mV since the cathodic protection system was put into service. CSE Cathodic protection standards. Check the current output parameters of the constant potential instrument. The output current is 10 times larger than that of other normal operating circuits. Through the on-site power feeding test, it is still difficult to achieve the polarization potential of some areas. It is now necessary to investigate the cathodic protection failure of the station.

[0083] (1) Before conducting on-site testing, prepare the relevant equipment and materials required for on-site testing, including a multimeter, copper sulfate reference electrode, and cables, etc. Then consult the design data, construction data, and completion data of the protected site to clarify the basic data of the protected structure of the protected site, including geometric dimensions, coating conditions, relative position, burial depth, lightning protection and grounding system, etc., and conduct an actual on-site inspection to check the relevant data and clarify whether the site has the conditions for temporary excavation.

[0084] (2) First, turn off the impressed current cathodic protection system to ensure that the entire system is in a natural state. Figure 3 The test points shown in the figure are tested for natural potential distribution. The test results are shown in Figure 4 As shown, select the area where the pipeline has a more positive potential to the ground.

[0085] (3) Carry out local excavation in the selected area, dig to the flexible anode body, and reveal the actual position and status of the anode and pipeline.

[0086] (4) Figure 5 As shown in the figure, the flexible anode exposed by excavation was partially disconnected. The change of ground potential before and after disconnection was measured. The test results are shown in Figure 6 As shown. Before and after the measurement, the potential of 1# and 2# anodes were both -0.18V CSE After disconnection, the potential of anode 1# to ground shifts negatively to -0.45V CSE , 2# anode positive shift to -0.10V CSE If the anode body potential shifts more positively, it indicates that the anode is far away from the overlap position; if the potential shifts negatively, it indicates that the anode is close to the overlap position.

[0087] (5) According to the change of potential, gradually reduce the range of the overlap point. Further excavate the area where the flexible anode potential is negatively offset and measure the anode-to-ground potential. The test results are as follows: Figure 7 As shown in the figure, the ground potential of the 1# flexible anode reaches the most negative value when it is close to the valve group area. Then, excavation is carried out near the test point until the specific overlap position is found.

[0088] (6) After confirming the overlapping point, perform insulation and sealing treatment on the area to prevent the anode and the pipeline from overlapping again.

[0089] (7) Restore the cathodic protection system and conduct another test to ensure that the pipeline and anode potentials have returned to normal after treatment. Record the potential changes of each test point before and after treatment to ensure that the potential after recovery meets the standard. Figure 8 As shown, it can be seen that after the overlap point treatment, the pipeline potential to ground is restored to the natural potential of the pipeline.

[0090] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for on-site inspection of the joint between a flexible anode and a pipeline, characterized in that: include: Turn off the flexible anode impressed current cathodic protection power supply device; Determine appropriate test points based on pipeline and flexible anode distribution; Measuring the potential of the buried pipeline to the ground at the test point to obtain pipeline-to-ground potential test data; According to the distribution of pipelines and flexible anodes, combined with the pipeline-to-ground potential test data, select areas where the pipeline-to-ground potential meets the preset rules for local excavation until the flexible anode body is exposed; Measure the ground potential of both sides of the flexible anode to obtain the ground potential test data before both sides of the flexible anode are disconnected; Determine the local disconnection position of the flexible anode, disconnect the flexible anode, measure the ground potential of both sides of the flexible anode, and obtain the ground potential test data after both sides of the flexible anode are disconnected; Determine the side with abnormal potential change according to the positive and negative potential changes in the ground potential test data before the two sides of the flexible anode are disconnected and the ground potential test data after the two sides of the flexible anode are disconnected; Excavation is carried out along the pipeline on the side where the potential changes abnormally, and the distribution of the flexible anode potential to the ground is tested. The overlapping point is determined based on the negative deviation trend of the flexible anode potential to the ground.

2. The method according to claim 1, characterized in that Also includes: Disconnect the overlapping point to eliminate the overlapping failure between the flexible anode and the pipeline.

3. The method according to claim 2, characterized in that Also includes: The treatment effect was confirmed by potential testing.

4. The method according to claim 1, characterized in that The measuring of the buried pipeline-to-ground potential at the test point to obtain pipeline-to-ground potential test data comprises: Lead out a wire from the ground metal structure that is electrically connected to the underground pipeline and connect it to the red probe of the multimeter; Connect one end of another long wire to the black test lead of a multimeter, and connect the other end of the other wire to a temporary reference electrode, wherein the temporary reference electrode is a copper / copper sulfate reference electrode, and place the copper / copper sulfate reference electrode on the moist soil directly above the pipeline; The multimeter is adjusted to the DC voltage position, and the value of the multimeter is recorded as pipeline-to-ground potential test data.

5. The method according to claim 1, characterized in that The method of selecting a pipeline to perform local excavation in an area where the ground potential meets a preset rule includes: The corresponding test points of the measured pipeline-to-ground potential are analyzed, and the area with relatively positive pipeline-to-ground potential is selected. Local excavation is carried out along the pipeline and anode according to the construction drawings during the construction of the cathodic protection system. The excavation size ensures that personnel can enter to perform measurements and disconnect operations, and the excavation depth is to expose the pipeline and flexible anode body.

6. The method according to claim 1, characterized in that The measuring of the ground potential of both sides of the flexible anode to obtain the ground potential test data of both sides of the flexible anode before disconnection includes: Lead a wire from the flexible anode body in the excavation pit to the red probe of the multimeter; Connect one end of another long wire to the black test lead of a multimeter, and connect the other end of the other long wire to a temporary reference electrode, wherein the temporary reference electrode is a copper / copper sulfate reference electrode, and place the copper / copper sulfate reference electrode on moist soil near the anode; Adjust the multimeter to the DC voltage position, and record the value of the multimeter as the ground potential test data before the two sides of the flexible anode are disconnected; The measuring of the ground potential of both sides of the flexible anode to obtain the ground potential test data after both sides of the flexible anode are disconnected includes: Lead a wire from the flexible anode body to the red probe of the multimeter; Connect one end of another long wire to the black test lead of a multimeter, and connect the other end of the other long wire to a temporary reference electrode, wherein the temporary reference electrode is a copper / copper sulfate reference electrode, and place the copper / copper sulfate reference electrode on moist soil near the anode; The multimeter is adjusted to the DC voltage position, and the value of the multimeter is recorded as the ground potential test data after the two sides of the flexible anode are disconnected.

7. The method according to claim 4 or 6, characterized in that: The error of the copper sulfate reference electrode does not exceed ±5mV.

8. The method according to claim 1, characterized in that Also includes: Test the self-corrosion potential; The test of self-corrosion potential includes: The multimeter is used to test the pipeline potential. The multimeter has a filtering function and its internal impedance is not less than 10MΩ.

9. The method according to claim 1, characterized in that: The area that meets the preset rules is: an area with a relatively positive potential, and the relatively positive potential is compared with the normal potential of this type of material in general soil.

10. The method according to any one of claims 1 to 9, characterized in that: The material of the pipeline is carbon steel material, and the flexible anode is a mixed metal oxide flexible anode.

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