Grounding grid corrosion detection method

Abstract

The invention relates to the technical field of grounding grid corrosion detection, in particular to a grounding grid corrosion detection method which comprises the following steps: arranging a transmitting coil and a receiving coil on the same plane to obtain the position of a grounding grid and arranging a measuring line parallel to grounding flat steel; adopting transient electromagnetic equipment to excite a transmitting coil, and enabling a receiving coil to acquire a voltage signal; carrying out preliminary analysis on the collected data, and judging whether corrosion defects exist or not; and drawing an apparent resistivity profile map according to the collected data, and determining corrosion defect positions and corrosion degrees. The grounding grid corrosion detection device has the beneficial effects that the transmitting coils which are reversely connected in series and the receiving coil at the midpoint are arranged on the same plane, so that primary field interference is effectively weakened, early secondary field signals are accurately detected, and the grounding grid corrosion detection precision is improved. The three coils are coplanar and simple in structure, large emission magnetic moment is guaranteed, and meanwhile high detection sensitivity is achieved. Through an apparent resistivity profile map, the corrosion position and degree can be accurately determined, and a scientific basis is provided for grounding grid maintenance.

Description

Technical Field

[0001] The invention relates to the technical field of grounding grid corrosion detection, in particular to a grounding grid corrosion detection method. Background Art

[0002] The basic principle of transient electromagnetic method is to transmit electromagnetic pulse signals through the transmitting coil, and then measure the attenuation characteristics of the induced electromagnetic field in the formation through the receiving coil. Changes in the corrosion state of the grounding grid will lead to differences in the induced voltage, which in turn affects the size and attenuation rate of the induced magnetic field. By analyzing the time domain variation curve of the induced electromagnetic field, the corrosion degree and location of the grounding grid can be inferred. The attenuation process of the electromagnetic field is generally divided into early, middle and late stages. The early electromagnetic field contains more shallow detection information, which is suitable for detecting corrosion defects of the grounding grid.

[0003] However, this information is mainly contained in the secondary field induced by the underground grounding grid. The strong primary field response overwhelms the secondary field signal, reducing the accuracy of grounding grid corrosion detection. Existing methods for eliminating the primary field, such as the compensation structure coil, have limited receiving coil size, no effective receiving area, and loss of the receiving coil's bandwidth; the reverse series connection of the two transmitting coils of the anti-flux structure coil still severely weakens the primary field, resulting in insufficient transmitting magnetic moment and reduced detection sensitivity. Existing technologies make it difficult to maintain a high detection sensitivity while weakening the influence of the primary field, which seriously restricts the development of transient electromagnetic for grounding grid corrosion detection. Summary of the invention

[0004] In view of the above problems or problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the object of the present invention is to provide a grounding grid corrosion detection method, which can weaken the influence of the primary field without losing the effective receiving area and ensure a larger emission magnetic moment when there are corrosion defects.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for detecting corrosion of a grounding grid, which comprises arranging a transmitting coil and a receiving coil on the same plane, obtaining the position of the grounding grid and arranging a measuring line parallel to the grounding flat steel;

[0007] A transient electromagnetic device is used to excite the transmitting coil so that the receiving coil collects the voltage signal;

[0008] Conduct preliminary analysis on the collected data to determine whether there are corrosion defects;

[0009] Draw the apparent resistivity profile based on the collected data to determine the location of the corrosion defect and the extent of corrosion.

[0010] As a preferred solution of the grounding grid corrosion detection method of the present invention, the transmitting coil refers to two identical transmitting coils connected in series in reverse order in the same plane, and the receiving coil refers to a receiving coil arranged at the midpoint of the line connecting the centers of the two coils.

[0011] As a preferred solution of the ground grid corrosion detection method of the present invention, the receiving coil and the transmitting coil are coplanar but have no crossing part.

[0012] As a preferred solution of the grounding grid corrosion detection method of the present invention, obtaining the location distribution of the grounding grid refers to obtaining the grounding grid topology and specific location based on the substation grounding grid design drawings.

[0013] As a preferred solution of the grounding grid corrosion detection method of the present invention, the measuring line is parallel to the grounding flat steel to ensure that the transmitting coil and the receiving coil can move along the direction of the grounding grid.

[0014] As a preferred solution of the grounding grid corrosion detection method of the present invention, the transient electromagnetic device includes a transmitter, a collection module, an amplifying circuit, a filtering circuit, and a host computer.

[0015] As a preferred solution of the grounding grid corrosion detection method of the present invention, the preliminary analysis method of the collected data is to extract the early signal of the induced voltage of the receiving coil based on the empirical value T, and obtain the maximum signal amplitude A. If A≥T, it is determined that there is a corrosion defect in the grounding grid section.

[0016] As a preferred embodiment of the grounding grid corrosion detection method of the present invention, the apparent resistivity profile drawing method includes: the induced voltage signal V of the receiving coil that is judged to have corrosion defects satisfies the following equation:

[0017]

[0018] Among them, t is time, a is the radius of the transmitting coil, erf is the error function, μ0 is the vacuum permeability, I is the emitted pulse current, and u is the transient field parameter, which corresponds to the apparent resistivity ρ as follows:

[0019]

[0020] Substitute the solved transient field parameter u into the above formula for calculation to obtain the curve of apparent resistivity ρ changing with time, that is, the apparent resistivity curve.

[0021] As a preferred solution of the grounding grid corrosion detection method of the present invention, the apparent resistivity curve is calculated by the following formula:

[0022]

[0023] Among them, ρr is the apparent resistivity used for imaging, σ is the conductivity of the uniform half space, μ0 is the magnetic permeability of vacuum, t j and t i are two adjacent time points in the apparent resistivity curve, ρ j and ρ i is the corresponding apparent resistivity, t ji is the average of two time points, d j and d i is the depth d corresponding to the two time points, H r is the same as ρ r The corresponding visual depth, 0.441 is the optimization coefficient.

[0024] As a preferred embodiment of the grounding grid corrosion detection method of the present invention, the apparent resistivity profile is imaged according to the calculation results of the apparent resistivity and apparent depth, and the corrosion position and corrosion degree are determined according to the apparent resistivity profile.

[0025] Beneficial effects of the present invention: The present invention effectively weakens the primary field interference, accurately detects the early secondary field signal, and improves the accuracy of grounding grid corrosion detection by arranging the transmitting coils connected in series in reverse on the same plane and the receiving coils at the midpoint. The three coils are coplanar and simple in structure, which ensures a large transmitting magnetic moment and high detection sensitivity. The corrosion position and degree can be accurately determined through the apparent resistivity profile, providing a scientific basis for grounding grid maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0027] Figure 1 Schematic diagram of the overall process of grounding grid corrosion detection method.

[0028] Figure 2 Schematic diagram of grounding grid layout for grounding grid corrosion detection method.

[0029] Figure 3 Schematic diagram of the receiving coil induced voltage curve of the ground grid corrosion detection method. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0033] Example 1

[0034] Reference Figure 1 to Figure 3 , is an embodiment of the present invention, which provides a grounding grid corrosion detection method, which can weaken the influence of the primary field without losing the effective receiving area, and also ensures a larger emission magnetic moment when there are corrosion defects.

[0035] Specifically, by arranging the transmitting coil and the receiving coil on the same plane, the position of the grounding grid is obtained and a measuring line parallel to the grounding flat steel is arranged;

[0036] A transient electromagnetic device is used to excite the transmitting coil so that the receiving coil collects the voltage signal;

[0037] Conduct preliminary analysis on the collected data to determine whether there are corrosion defects;

[0038] Draw the apparent resistivity profile based on the collected data to determine the location of the corrosion defect and the extent of corrosion.

[0039] It should be noted that the diameter of the transmitting coil is 1m, the diameter of the receiving coil is 0.5m, and the distance between the centers of each two coils is 1m. Figure 2 As shown, a grounding grid is laid, wherein a section of the grounding grid is composed of a flat steel grid of 8m×8m.

[0040] Furthermore, the transmitting coil refers to two identical transmitting coils arranged in series in opposite directions in the same plane, and the receiving coil refers to a receiving coil arranged at the midpoint of a line connecting the centers of the two coils.

[0041] Furthermore, the receiving coil is coplanar with the transmitting coil but has no crossing portion.

[0042] Furthermore, obtaining the location distribution of the grounding grid refers to obtaining the topological structure and specific location of the grounding grid according to the substation grounding grid design drawing.

[0043] Furthermore, the measuring line is parallel to the grounding flat steel, ensuring that the transmitting coil and the receiving coil can move along the direction of the grounding grid.

[0044] Furthermore, the transient electromagnetic device includes a transmitter, an acquisition module, an amplifying circuit, a filtering circuit, and a host computer.

[0045] Furthermore, a preliminary analysis method for the collected data is to extract the early signal of the induced voltage of the receiving coil based on the empirical value T, and obtain the maximum amplitude A of the signal. If A≥T, it is determined that there is a corrosion defect in the grounding grid section.

[0046] It should be noted that the measured induced voltage curve is as follows Figure 3 As shown, set the empirical value T = 5 × 10 -5 V, the maximum amplitude of the early induced voltage signal without defects is 9.55×10 -6 V, the maximum amplitude of the early induced voltage signal when there is a defect is 1.6×10 -4 V, can accurately identify defects based on the judgment criteria.

[0047] Furthermore, the method for drawing the apparent resistivity profile includes determining that the induced voltage signal V of the receiving coil where the corrosion defect is determined satisfies the following equation:

[0048]

[0049] Among them, t is time, a is the radius of the transmitting coil, erf is the error function, μ0 is the vacuum permeability, I is the emitted pulse current, and u is the transient field parameter, which corresponds to the apparent resistivity ρ as follows:

[0050]

[0051] Substitute the solved transient field parameter u into the above formula for calculation to obtain the curve of apparent resistivity ρ changing with time, that is, the apparent resistivity curve.

[0052] Furthermore, according to the resistivity curve, the calculation formula is as follows:

[0053]

[0054] Among them, ρ r is the apparent resistivity used for imaging, σ is the conductivity of the uniform half space, μ0 is the magnetic permeability of vacuum, t j and t i are two adjacent time points in the apparent resistivity curve, ρ j and ρ i is the corresponding apparent resistivity, t ji is the average of two time points, d j and d i is the depth d corresponding to the two time points, H r is the same as ρ rThe corresponding visual depth, 0.441 is the optimization coefficient.

[0055] Furthermore, the apparent resistivity profile is imaged according to the calculation results of the apparent resistivity and the apparent depth, and the corrosion position and the corrosion degree are determined according to the apparent resistivity profile.

[0056] It should be noted that if Figure 3 As shown in the figure, the horizontal axis represents time (in microseconds, μs), the vertical axis represents voltage (in volts, V), and the voltage value has been scaled to 10 -4 The solid line in the figure represents the induced voltage curve of the defective grounding grid, and the dotted line represents the induced voltage curve of the non-defective grounding grid.

[0057] Specifically, the initial response shown in the figure is that when the time is close to 0 μs, both curves show a sharp voltage peak, which is the voltage induced in the receiving coil by the transient electromagnetic field generated by the transmitting coil.

[0058] Among them, the early signal is between 0μs and 50μs, the defective ground grid (solid line) shows an obvious negative voltage, while the non-defective ground grid (dashed line) quickly returns to a level close to 0V. This shows that the defective ground grid exhibits different electromagnetic responses in the early signal.

[0059] The mid-term signal is between 50μs and 200μs, and both curves are relatively stable with the voltage close to 0V, which may indicate that during this period, the attenuation characteristics of the electromagnetic field are similar in the defective and non-defective grounding grids.

[0060] After 200μs, the defective grounding grid (solid line) again shows an obvious voltage drop, forming a negative spike, while the non-defective grounding grid (dashed line) remains at a level close to 0V. The negative spike is due to the abnormal attenuation of the electromagnetic field caused by the defect of the grounding grid.

[0061] By analyzing the signals according to the above description, it is possible to determine whether the grounding grid has corrosion defects by comparing the maximum amplitudes of the early signals of these curves. That is, if the amplitude of the early signal exceeds the threshold T set based on experience, it can be determined that the grounding grid section has corrosion defects.

[0062] In summary, the present invention effectively weakens the primary field interference, accurately detects the early secondary field signal, and improves the accuracy of grounding grid corrosion detection by arranging the transmitting coils connected in series in reverse on the same plane and the receiving coils at the midpoint. The three coils are coplanar and simple in structure, which ensures a large transmitting magnetic moment and high detection sensitivity. The corrosion location and degree can be accurately determined through the apparent resistivity profile, providing a scientific basis for grounding grid maintenance.

[0063] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible without substantially departing from the novel teachings and advantages of the subject matter described in the application (e.g., mounting arrangements, use of materials, color, changes in orientation, etc.). For example, the element shown as integrally formed may be composed of a plurality of parts or elements, the position of the element may be inverted or otherwise changed, and the nature or number or position of the discrete element may be altered or changed. Therefore, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be changed or reordered according to an alternative embodiment. In the claims, any "bracket plus function" clause is intended to cover the structure of the execution function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the present invention is not limited to a specific embodiment, but extends to a variety of modifications that still fall within the scope of the appended claims.

[0064] Additionally, in an effort to provide a concise description of example embodiments, all features of an actual implementation may not be described.

[0065] It should be understood that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but for those of ordinary skill having the benefit of this disclosure, the development effort will be a routine task of design, fabrication, and production without undue experimentation.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A grounding grid corrosion detection method, characterized in that: include, By arranging the transmitting coil and the receiving coil on the same plane, the grounding grid position is obtained and the measuring line parallel to the grounding flat steel is arranged; A transient electromagnetic device is used to excite the transmitting coil so that the receiving coil collects the voltage signal; Conduct preliminary analysis on the collected data to determine whether there are corrosion defects; Draw the apparent resistivity profile based on the collected data to determine the location of the corrosion defect and the extent of corrosion.

2. The grounding grid corrosion detection method according to claim 1, characterized in that: The transmitting coil refers to two identical transmitting coils connected in series in opposite directions arranged in the same plane, and the receiving coil refers to a receiving coil arranged at the midpoint of the line connecting the centers of the two coils.

3. The grounding grid corrosion detection method according to claim 2, characterized in that: The receiving coil is coplanar with the transmitting coil but has no crossing portion.

4. The grounding grid corrosion detection method according to claim 3, characterized in that: The obtaining of the grounding grid location distribution refers to obtaining the grounding grid topology and specific location according to the substation grounding grid design drawing.

5. The grounding grid corrosion detection method according to claim 4, characterized in that: The measuring line is parallel to the grounding flat steel, ensuring that the transmitting coil and the receiving coil can move along the direction of the grounding grid.

6. The grounding grid corrosion detection method according to any one of claims 2 to 5, characterized in that: The transient electromagnetic device comprises a transmitter, a collection module, an amplifying circuit, a filtering circuit, and a host computer.

7. The grounding grid corrosion detection method according to claim 6, characterized in that: The method for performing preliminary analysis on the collected data is to extract the early signal of the induced voltage of the receiving coil based on the empirical value T, obtain the maximum amplitude A of the signal, and if A≥T, it is determined that there is a corrosion defect in the grounding grid section.

8. The grounding grid corrosion detection method according to claim 7, characterized in that: The method for drawing the apparent resistivity profile includes determining that the induced voltage signal V of the receiving coil where the corrosion defect exists satisfies the following equation: Among them, t is time, a is the radius of the transmitting coil, erf is the error function, μ0 is the vacuum permeability, I is the emitted pulse current, and u is the transient field parameter, which corresponds to the apparent resistivity ρ as follows: Substitute the solved transient field parameter u into the above formula for calculation to obtain the curve of apparent resistivity ρ changing with time, that is, the apparent resistivity curve.

9. The grounding grid corrosion detection method according to claim 8, characterized in that: The apparent resistivity curve is calculated by the following formula: Among them, ρ r is the apparent resistivity used for imaging, σ is the conductivity of the uniform half space, μ0 is the magnetic permeability of vacuum, t j and t i are two adjacent time points in the apparent resistivity curve, ρ j and ρ i is the corresponding apparent resistivity, t ji is the average of two time points, d j and d i is the depth d corresponding to the two time points, H r is the same as ρ r The corresponding visual depth, 0.441 is the optimization coefficient.

10. The grounding grid corrosion detection method according to claim 9, characterized in that: The apparent resistivity profile is imaged according to the calculation results of the apparent resistivity and the apparent depth, and the corrosion position and the corrosion degree are determined according to the apparent resistivity profile.

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