Simplified calculation method and device for galvanic corrosion rate of large-scale complex grounding system

Abstract

The application discloses a large-scale complex grounding system galvanic corrosion rate simplified calculation method and device, first, each grounding body of the large-scale complex grounding system is segmented, and a galvanic corrosion calculation model of the large-scale complex grounding system is constructed based on an electrochemical corrosion principle, a moment method and a node voltage method, then the Taylor formula is used to linearize and approximate the galvanic corrosion calculation model, and the potential drop on the grounding conductor is ignored, and then the galvanic corrosion current density calculation problem is converted into a grounding system current density calculation problem under the action of a constant voltage source, and the galvanic corrosion rate of the grounding system is calculated. The application can quantitatively calculate the galvanic corrosion rate under the conditions of any complex grounding system arrangement, any grounding body material type and kind and any soil structure.

Description

Technical Field

[0001] This invention belongs to the field of electrical engineering technology, specifically relating to a simplified calculation method and apparatus for galvanic corrosion rate in large-scale complex grounding systems. Background Technology

[0002] Large-scale complex grounding systems refer to grounding systems composed of a large number of metallic conductors, where the maximum diagonal is often much larger than (e.g., 10,000 times or more) the conductor diameter, such as the grounding grids of power plants / substations and the grounding systems of urban utility tunnels. Grounding systems, as channels for discharging lightning currents and fault currents, are crucial facilities for ensuring the safety of equipment and personnel. For economic reasons, most grounding grids in my country's existing power plants use galvanized steel; however, due to the excellent corrosion resistance and conductivity of copper conductors, their use in power plant grounding grid construction is continuously increasing. For resistance reduction and other considerations, the grounding grids of power plants and substations are often connected to nearby natural grounding bodies. If the two use different metallic materials, galvanic corrosion will occur, posing a serious threat to the safe and stable operation of the power plant and surrounding facilities. However, there is currently no method to calculate the galvanic corrosion rate of large-scale complex grounding systems. Furthermore, cathodic protection of grounding facilities is essentially a galvanic corrosion problem. Therefore, to design effective and reasonable cathodic protection schemes, it is urgent to propose a method to calculate the galvanic corrosion rate of large-scale complex grounding systems.

[0003] Grounding systems typically consist of numerous slender grounding conductors with radii much smaller than the maximum diagonal of the entire system. Furthermore, the governing equations for galvanic corrosion are highly nonlinear. Therefore, commonly used finite element and boundary element methods cannot be directly applied to the galvanic corrosion analysis of large-scale, complex grounding systems. They can only perform quantitative calculations by examining a small area of ​​galvanic pairs near the connection points, which is insufficient to guide practical engineering. Currently, qualitative analysis of galvanic corrosion in large-scale, complex grounding systems is mainly based on experimentally obtained corrosion characteristics. However, qualitative conclusions alone are insufficient to guide the prediction of the lifespan and the design of anti-corrosion measures for large-scale, complex grounding systems.

[0004] Therefore, there is an urgent need to propose a method that can quantitatively analyze the corrosion rate of galvanic electrodes in large-scale complex grounding systems, so as to provide a basis for predicting the remaining service life of grounding systems and designing anti-corrosion measures. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to address the difficulty in calculating the galvanic corrosion rate of large-scale complex grounding systems, the present invention provides a method and apparatus for calculating the corrosion rate, which can quantitatively calculate the galvanic corrosion rate of large-scale complex grounding systems.

[0006] The simplified calculation method for galvanic corrosion rate in a large-scale complex grounding system according to the present invention includes the following steps:

[0007] S1. Based on the method of moments and the principle of electrochemical corrosion, each grounding body in a large-scale complex grounding system is divided into conductor segments, and the mathematical relationship between the potential and the current of each grounding conductor segment is constructed. At the same time, the mathematical relationship between the node potential and the current of each node in each conductor segment is constructed using the node voltage method. Then, based on the mathematical relationship between the potential of each conductor segment and the node potential of the conductor segment, as well as the relationship between the current of each conductor segment and the current of each node in the conductor segment, a calculation model for galvanic corrosion of a large-scale complex grounding system is obtained.

[0008] S2. The calculation model of galvanic corrosion of a large-scale complex grounding system is linearized and approximated to obtain a set of linear equations for calculating the current dissipation of each grounding conductor segment. The set of equations is used as the linear equations for calculating the total corrosion current of each grounding conductor segment. The potential drop on the grounding conductor is ignored. The problem of calculating the galvanic corrosion current density is transformed into the problem of calculating the current dissipation of the grounding system under the action of a constant voltage source, so as to realize the calculation of the total corrosion current of each grounding conductor segment.

[0009] S3. Calculate the corresponding corrosion current density using the total corrosion current of each grounding conductor segment, and calculate the corrosion rate of each grounding conductor segment based on Faraday's law to obtain the galvanic corrosion rate distribution of the entire grounding system. Then, verify the effectiveness of the linearization approximation based on the corrosion current density calculation results: when the approximation conditions are met, the corrosion rate calculation result is the actual corrosion rate of the grounding system; otherwise, the calculation result is only the upper and lower limits of the actual corrosion rate.

[0010] Furthermore, in S1, the calculation model for galvanic corrosion is as follows:

[0011]

[0012]

[0013] In the above formula, η represents the overpotential η of each grounded conductor segment. j The vector formed; E corr The corrosion potential E of each grounding conductor section jcorr The vector consists of: M1, the number of conductor segments directly buried in the soil; M2, the number of conductor segments with anti-corrosion coating or exposed to air; B, C, R Z This is a 4-block matrix introduced for ease of writing, and its expression is as follows:

[0014]

[0015] In the above formula, P is the identity matrix; L is a matrix with all elements equal to zero; [R mj [] represents a matrix composed of mutual resistances, where the element in the m-th row and j-th column is R. mj ;P, L and [R mjThe two subscripts ] represent the row number and column number, respectively, for example It is a matrix with M1 rows and M2 columns, all of which are zero.

[0016] Furthermore, in S2, the Taylor formula is used to linearize the calculation model of galvanic corrosion in large-scale complex grounding systems.

[0017] Furthermore, in S2, the linear equations for calculating the total corrosion current of each grounded conductor segment are as follows:

[0018]

[0019] Among them, R' z As an intermediate variable; It is a matrix with M1+M2 rows, 1 column, and all elements being 1; This is a matrix with 1 row and M1+M2 columns, all elements being 1; M1 is the number of conductor segments directly buried in the soil; M2 is the number of conductor segments coated with insulation and placed in the air; I is the current dissipated by the conductor segments. j The vector formed; E0 is the absolute electrode potential of the standard hydrogen electrode; u0 is the node potential of node 1; E corr The corrosion potential E of each grounding conductor section jcorr The vector formed; It is a matrix with M2+1 rows, 1 column, and all elements being 0;

[0020]

[0021] Where P is the identity matrix; L is a matrix with all elements equal to zero; P, L, and [R] mj The two subscripts ] represent the row number and column number, respectively, for example It is a matrix with M1 rows and M2 columns, all of which are zero.

[0022] Furthermore, in S3, the approximate condition is:

[0023]

[0024] Where, η j Let β1 be the overpotential of conductor segment j, and β2 be the Tafel slopes of the anode and cathode, respectively; i L S is the limiting diffusion current density; j Let i be the surface area of ​​the j-th conductor segment; j Let be the galvanic corrosion current density on the j-th conductor segment.

[0025] Furthermore, in S3, the formula for calculating the corrosion rate of each grounding conductor segment is as follows:

[0026]

[0027] Where n is the electrochemical reaction equivalent; F is the Faraday constant; A is the molar mass of the corroded substance; v j Let be the average corrosion rate on the j-th conductor segment, g / (m 2 ·h).

[0028] Furthermore, in S3, when the simplification conditions are not met, according to R... p When ≠0, the total corrosion current of each grounding conductor segment is calculated using a linear equation set, and the lower limit of the corrosion rate increase due to galvanic corrosion in the grounding system is calculated based on the total corrosion current of each grounding conductor segment; according to R p When =0, the total corrosion current of each grounding conductor segment is calculated by the linear equation system of the total corrosion current of each grounding conductor segment, and the upper limit of the corrosion rate increase of the grounding system due to galvanic corrosion is calculated based on the total corrosion current of each grounding conductor segment.

[0029] A simplified calculation device for galvanic corrosion rate in a large-scale complex grounding system, comprising:

[0030] Input module: Used to input soil resistivity and electrochemical corrosion parameters;

[0031] Corrosion current density calculation module: used to calculate corrosion current density based on soil resistivity and electrochemical corrosion parameters;

[0032] Galvanic corrosion rate distribution calculation module: used to calculate the galvanic corrosion rate distribution based on corrosion current density.

[0033] A computer device includes an electrically connected memory and a processor, the memory storing a computer program executable on the processor, wherein when the processor executes the computer program, it implements the steps of the method according to any one of claims 1-8.

[0034] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0035] This invention constructs a calculation model for galvanic corrosion in large-scale complex grounding systems based on the principles of electrochemical corrosion, the method of moments, and the nodal voltage method. It then uses Taylor's formula to linearize the model, and by neglecting the potential drop on the grounding conductor, transforms the original galvanic corrosion problem into a calculation problem of the current density of the grounding system under a constant voltage source, thus realizing the calculation of the galvanic corrosion rate in large-scale complex grounding systems. It can quantitatively calculate the galvanic corrosion rate under any complex grounding system layout, any type and variety of grounding electrode material, and any soil structure. Practical grounding projects require an insulating layer within at least 2 meters of the connection point of dissimilar metal conductors, resulting in a relatively low galvanic corrosion current density, which usually meets the application conditions of this invention. Even when these conditions are not met, the upper and lower limits of the galvanic corrosion rate for each grounding conductor can still be obtained according to this invention. Attached Figure Description

[0036] Figure 1 This is a flowchart of the process of the present invention;

[0037] Figure 2 A schematic diagram of current dissipation from a grounded conductor;

[0038] Figure 3 A model for calculating galvanic corrosion rate;

[0039] Figure 4 This is a schematic diagram showing the relationship between different potentials on a grounded conductor segment.

[0040] Figure 5a This is a schematic diagram of a galvanic corrosion problem.

[0041] Figure 5b A schematic diagram illustrating the calculation of current density in a grounding system under constant voltage source conditions.

[0042] Figure 6 for Figure 5b A schematic diagram of the computational model;

[0043] Figure 7 This is a schematic diagram of a copper / steel galvanic corrosion experiment.

[0044] Figure 8a shows the experimental and simulated values ​​of the total galvanic corrosion current;

[0045] Figure 8b shows the calculated value of the maximum corrosion current density;

[0046] Figure 8c shows the calculated value of the maximum overpotential;

[0047] Figure 9 The model for calculating galvanic corrosion rate is constructed using the method of moments software.

[0048] Figure 10a For R pGalvanic corrosion current density distribution on the steel grounding grid when = 0;

[0049] Figure 10b For R p Galvanic corrosion current density distribution on the steel grounding grid when ≠0;

[0050] Figure 11 The rate of decrease in the diameter of the steel grounding grid conductor caused by galvanic corrosion;

[0051] Figure 12 This is a schematic diagram of the computing device of the present invention;

[0052] Figure 13 A schematic diagram of the structure of the computer device provided for the present invention. Detailed Implementation

[0053] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0054] In the description, "grounding conductor" refers to a metal conductor buried in the soil, "grounding system" refers to a device consisting of a large number of grounding conductors buried in the soil, and "site" refers to the location where the power station's grounding system is buried.

[0055] This invention determines soil resistivity and electrochemical corrosion parameters based on the characteristics of soil and conductor materials. It segments each grounding electrode in a large-scale complex grounding system using the method of moments, and, combining the principles of electrochemical corrosion, constructs a mathematical relationship between the potential of each grounding conductor segment and the stray current (i.e., the total corrosion current of each conductor segment). Furthermore, it uses the nodal voltage method to construct a mathematical relationship between the nodal potential of each conductor segment and the nodal stray current. Based on the mathematical relationships between the potential of each conductor segment and the nodal potential of the conductor segment, as well as between the stray current of each conductor segment and the stray current of the conductor segment and the nodal stray current of the conductor segment, a calculation model for galvanic corrosion in a large-scale complex grounding system is obtained. The Taylor formula is then used. The galvanic corrosion calculation model is linearized and the potential drop on the grounding conductor is ignored. This yields a set of linear equations for calculating the total corrosion current of each grounding conductor segment, transforming the galvanic corrosion current density calculation problem into the grounding system current density calculation problem under the action of a constant voltage source. Finally, based on the total corrosion current calculation results of each conductor segment, Faraday's law is used to calculate the galvanic corrosion rate distribution of the entire grounding system, and the effectiveness of the linearization approximation is verified. If the calculation method is effective, the calculation result is the actual galvanic corrosion rate of the grounding system; otherwise, the calculation result can only represent the upper and lower limits of the actual galvanic corrosion rate of the grounding system.

[0056] The core technology of this invention is based on the principle of electrochemical corrosion, the method of moments, and the nodal voltage method. It constructs a mathematical relationship between the potential of each grounding conductor segment and the corrosion current, and uses Taylor's formula for linearization approximation. Then, by neglecting the potential drop on the grounding conductor, the problem of calculating the galvanic corrosion current density is transformed into the problem of calculating the current density of the grounding system under the action of a constant voltage source, so as to realize the calculation of the galvanic corrosion rate of complex grounding systems.

[0057] Example 1

[0058] Reference Figure 1 A simplified calculation method for galvanic corrosion rate in large-scale complex grounding systems includes the following steps:

[0059] Step 1: Based on the characteristics of the soil and conductor materials, determine the soil resistivity ρ and the electrochemical parameters of the grounding conductor, including the corrosion potential E. cor Polarization resistance R p Tafel slopes β1 and β2, limiting diffusion current density i L .

[0060] Step 2: Based on the method of moments and the principle of electrochemical corrosion, each grounding electrode in a large-scale complex grounding system is divided into conductor segments of a certain length, such as... Figure 2 As shown, the mathematical relationship between the potential of each grounding conductor segment and the stray current is constructed, such as... Figure 3 As stated above.

[0061] Figure 2 In the diagram, j represents the segment number of the conductor after segmentation. The specific length of the conductor segment should be determined based on a comprehensive consideration of computational accuracy and scale. The shorter the conductor segment, the higher the computational accuracy, but the longer the computation time required; n represents the endpoint number of the conductor segment; I j J represents the current dissipated in conductor segment j; n The current flowing into the ground from endpoint n is a virtual variable introduced for modeling calculations. This current does not exist in reality. Its relationship with the current dissipated in the conductor segment will be introduced later.

[0062] Figure 3 Middle, Y j η is the axial admittance of conductor segment j; j V is the overpotential of conductor segment j; j E represents the potential on the outer side of the electric double layer of conductor segment j; jcorr Let J be the corrosion potential of conductor segment j relative to the standard hydrogen electrode; E0 is the absolute electrode potential of the standard hydrogen electrode, which is an unmeasurable constant. This invention avoids solving for the absolute electrode potential by merging unknown variables.

[0063] The potential calculation formula for conductor segments M1 directly buried in the soil is as follows:

[0064]

[0065] In equation (1), E j R is the conductor potential of conductor segment j; mj The mutual resistance between conductor segment m and conductor segment j can be calculated using Green's function. During the calculation, the soil resistivity parameters of the environment where the grounding device is located are required.

[0066] Figure 4 The equation (1) shows the relationship between the potentials and corrosion current density. When the current dissipation is I... j At that time, the potential difference between the metallic conductor and the soil caused by the electric double layer is E. jcorr +E0+η j The thickness of the electric double layer is typically between 0.2 and 20 nm, which is much smaller than the conductor radius. Therefore, the influence of the electric double layer thickness will not be considered in the modeling and calculation process of this invention.

[0067] For the M2 conductor segments coated with an insulating layer and exposed to air, the formula for calculating the current dissipation is as follows:

[0068] I j =0 (2)

[0069] The mathematical relationships between the node potentials and node currents of each conductor segment are constructed using the nodal voltage method, as shown in equations (3) and (4):

[0070]

[0071]

[0072] In equations (3) and (4), N is the number of nodes; A is the non-augmented form of the correlation matrix; Y is the admittance matrix of each conductor segment; X is a vector composed of the voltages of all nodes except node 1; Q is a matrix with all elements equal to 1. For ease of representation, the size of the matrix is ​​indicated by two subscripts separated by commas, such as Q. N-1,1 This represents a matrix with N-1 rows and 1 column; i0 and u0 are the node current and potential of node 1, respectively. When using the calculation method proposed in this invention, any endpoint of the grounding body segment can be selected as node 1. However, for ease of interpretation of the model and calculation results, in this invention, one of the dissimilar metal connection points will be selected as node 1; U is the node voltage vector; J is the node current vector, which is formed by the current vector of all nodes. n Composition; W is a vector consisting of the currents of all nodes except node 1.

[0073] In using the method of moments, to ensure calculation accuracy, the divided conductor segments are usually short, typically less than 5% of the maximum diagonal length of the grounding grid. Therefore, the potential of each conductor segment can be approximated using the midpoint potential, which can be approximated as the average of the potentials at both ends of the node. Furthermore, the current dissipated at each node is approximately half the sum of the current dissipated in the connected conductor segments, i.e.:

[0074] E = KU (5)

[0075] J = K T I (6)

[0076]

[0077] In the formula, E is a vector composed of the potentials of the conductor segment; K is a matrix representing the connection relationship between the conductor segment and the endpoint, and the element in the j-th row and n-th column of the matrix is ​​K in formula (7). jn I is the current I scattered by all conductor segments. j The vector formed.

[0078] By combining equations (1) to (7), a calculation model for galvanic corrosion in a large-scale complex grounding system can be obtained:

[0079]

[0080]

[0081] In equation (8), η is the overpotential η of each grounded conductor segment. j The vector formed, E corr The corrosion potential E of each grounding conductor section jcorr The vectors formed by B, C, and R Z This is a 4-block matrix introduced for ease of writing; it has no physical meaning, and its expression is as follows:

[0082]

[0083] In equation (9), P is the identity matrix; L is a matrix with all elements equal to zero; [R mj [] represents a matrix composed of mutual resistances, where the element in the m-th row and j-th column is R. mj The two subscripts of the matrix represent the row number and the column number, respectively.

[0084] Step 3: Use Taylor's formula to linearize the calculation model (8) for galvanic corrosion of large-scale complex grounding systems, and then obtain the linear equation set for calculating the total corrosion current of each grounding conductor:

[0085]

[0086] In equation (10), the intermediate variable R' zas follows:

[0087]

[0088] In equation (11), S j R is the surface area of ​​the j-th conductor segment; pj Let be the polarization resistance of the j-th conductor segment.

[0089] From the remainder term of Taylor's formula, we know that in order to ensure the linearization in equation (10) is effective, the simplification condition that needs to be satisfied is:

[0090]

[0091] In equation (12a), β1 and β2 are the Tafel slopes of the anode and cathode, respectively; L i is the limiting diffusion current density; j Let R be the galvanic corrosion current density on the j-th conductor segment. It should be noted that, due to R... p When R ≠ 0, the total corrosion current of each conductor segment calculated by equation (10) is too small, while when R p When = 0, the total corrosion current of each conductor segment calculated by equation (10) is too large. Therefore, this invention will utilize equation (10) in R p The total corrosion current I of each conductor segment calculated under the condition that = 0. j Equation (12) is then verified. Furthermore, to simplify the calculation process, only the maximum values ​​of the overpotential and corrosion current density need to be verified.

[0092]

[0093] In equation (12b), η m-Rp＝0 and i m-Rp＝0 R respectively p The maximum overpotential and maximum galvanic corrosion current density are calculated by formula (10) when the value is 0.

[0094] When the overpotential is much smaller than the potential drop in the soil, the overpotential can be ignored. Then, using equation (10), in R... p Under the condition that = 0, the total corrosion current of each grounding conductor section can be calculated. The simplified condition that needs to be satisfied at this time is:

[0095]

[0096] In equation (13), I c-Rp＝0 and I c-Rp≠0 R respectively p =0 and R p When ≠0, the total galvanic corrosion current of the entire grounding system calculated by equation (10); i m-Rp≠0 For R p The maximum galvanic corrosion current density calculated by formula (10) when ≠0.

[0097] Step 4: Ignoring the potential drop on the grounded conductor, equation (10) can be further simplified to:

[0098]

[0099] Therefore, the problem of calculating the galvanic corrosion current density (such as...) can be solved. Figure 5a The problem is transformed into the calculation of the current density of a grounding system under constant voltage source (e.g.) Figure 5b ). Figure 5b The polarization potential between the electrode and the soil is no longer considered, and the polarization resistance is taken as the surface resistivity of the grounding electrode. Furthermore, the grounding system layout is the same as the original galvanic corrosion problem. Figure 5b The corresponding computational model is as follows Figure 6 As shown.

[0100] Depend on Figure 5b The calculated current density is the galvanic corrosion current density of each conductor in the grounding system. Obviously, after neglecting the axial voltage drop on the grounding conductor, the potential of each connection point is the same, and the connection point potential (u0-E0) is the corrosion potential of the grounding system relative to the standard hydrogen electrode.

[0101] For equation (14), the calculation of the current dissipation of each grounding conductor segment can be realized by using commonly used moment method calculation software (such as CDEGS), and then the galvanic corrosion current density of each grounding conductor segment can be obtained.

[0102] Step 5: When equation (12) holds true, according to R p When the current distribution is not equal to 0, the current distribution of each grounding conductor segment calculated by equation (14) is used to calculate the average galvanic corrosion rate on all conductor segments of the grounding system using Faraday's law, as shown in equation (15). The galvanic corrosion rate distribution of the entire grounding system is the result of the average galvanic corrosion rate v on all grounding conductor segments. j The vector formed by these vectors.

[0103]

[0104] Where, n is the electrochemical reaction equivalent; F is the Faraday constant, 26.8 A·h; A is the molar mass of the corroded substance, g / mol; v j Let be the average corrosion rate on the j-th conductor segment, g / (m 2 ·h).

[0105] When equation (12) is not true, but equation (13) is true, according to R p When the current is 0, the current of each grounding conductor segment calculated by equation (14) is used to calculate the distribution of corrosion rate of the grounding system due to galvanic corrosion using equation (15).

[0106] When considering polarization resistance, the corrosion current density calculated by the simplified model is too small. However, when overpotential is ignored (the polarization resistance in the simplified model is taken as zero), the corrosion current density calculated by the simplified model is too large, and the error increases with the increase of corrosion current density.

[0107] When neither equation (12) nor equation (13) holds true, according to R p When ≠0, the current dissipated in each grounding conductor segment calculated by equation (14) is used to calculate the lower limit of the corrosion rate increase in the grounding system due to galvanic corrosion using equation (15); based on R p When the current is 0, the current of each grounding conductor segment calculated by equation (14) is used to calculate the upper limit of the corrosion rate increase of the grounding system due to galvanic corrosion using equation (15).

[0108] Application Example 1

[0109] A simplified calculation method for galvanic corrosion rate in large-scale complex grounding systems includes the following steps:

[0110] Step 1, the setup for the galvanic corrosion test of copper / steel electrodes is as follows: Figure 7 As shown. Before the experiment, the resistivity of the soil used in the experiment was measured to be 45.99 Ω·m using the four-electrode method.

[0111] Figure 7 In order to increase the total galvanic corrosion current I c To improve measurement accuracy, copper electrode 2 uses a 16cm × 33cm copper plate and is positioned close to the right side of the experimental tank. To facilitate changing the electrode spacing d, steel electrode 1 is 16cm long and vertically arranged. The round steel bar was moved along the centerline of the experimental trough.

[0112] Under ambient temperature (25℃), the corrosion potentials of steel and copper electrodes in the experimental soil sample were tested using a Cu / CuSO4 reference electrode. The corrosion potential of the copper electrode was 0.348V (vs. SHE), and the corrosion potential of the steel electrode was -0.308V (vs. SHE). Referring to relevant literature, the electrochemical corrosion parameters of the copper / steel electrode in clay (pH=7) are shown in Table 1.

[0113] Table 1 Electrochemical corrosion parameters of copper / steel electrodes in soil

[0114]

[0115] Step 2: Using commonly used method of moments (MMT) calculation software (such as CDEGS), based on... Figure 7 Construct the corresponding copper / steel electrodes and connecting wires, and at the copper-steel connection points on the connecting wires, according to... Figure 5bA constant voltage source with a voltage magnitude equal to the corrosion potential is set, and the surface resistivity of the coating layer on the electrode and connecting wire is set to the value of the polarization resistance. The resistivity of the electrode and connecting wire is set to a very small value (1e-15Ω·m in this case; the specific value can be determined based on the conductor potential distribution in the calculation results. When the maximum potential difference of the same conductor is much smaller than the corrosion potential difference, the resistivity value at this time can be considered appropriate), and the corresponding soil model is set according to the soil resistivity test results. After that, the method of moments calculation software can automatically generate the linear equation system (14) and complete the calculation and solution to obtain the current density distribution on the electrode.

[0116] Step 3: Under different electrode spacings, use R p =0 and R p The calculation model for when ≠0 is used to calculate the distribution of galvanic corrosion current density (spreading current density) on the copper / steel electrode. The total corrosion current, maximum corrosion current density, and maximum overpotential flowing through the connecting wire are shown in Figures 8a, 8b, and 8c, respectively.

[0117] Step 4: As shown in Figure 8, when the electrode spacing is greater than 0.55m, equation (12) is difficult to hold, while equation (13) is basically true. Therefore, R can be used. p The corrosion current density calculated when = 0 is used to calculate the galvanic corrosion rate on the steel electrode. However, when the electrode spacing is less than 0.55m, equations (12) and (13) are difficult to satisfy, therefore only R can be used. p =0 and R p The results calculated when ≠0 are used as the upper and lower limits of the actual galvanic corrosion rate.

[0118] To verify the effectiveness of the galvanic corrosion calculation model, the total corrosion current I flowing from the copper electrode to the steel electrode was tested under different electrode spacings d. c The results are shown in Figure 8a. As can be seen from the figure, when R... p When R is not equal to 0, the calculated corrosion current is too small, while R p When the coefficient of corrosion current is 0, the calculated corrosion current is too high, and the error decreases as the corrosion current density decreases. When the electrode spacing is greater than 0.55m, the calculation results agree well with the experimental results. Therefore, the calculation method proposed in this invention can effectively calculate the galvanic corrosion rate.

[0119] Step 5: Based on the calculation results of the galvanic corrosion current density, analyze the increased corrosion rate due to galvanic corrosion. For example, when the electrode spacing is 0.67m, the total corrosion rate of the steel rod is v = 55.845g × 1.06mA / (2 × 26.8A·h) = 1.104mg / h.

[0120] Application Example 2

[0121] A simplified calculation method for galvanic corrosion rate in large-scale complex grounding systems includes the following steps:

[0122] Step 1: Use the four-pole method to test the soil parameters at the site and invert to obtain the layered soil model as shown in Table 2.

[0123] Table 2 Soil parameters at the site

[0124]

[0125] Under ambient temperature (25℃), the corrosion potential of soil samples collected in the field was tested using a Cu / CuSO4 reference electrode. The corrosion potential of the copper conductor was found to be 0.346V (vs. SHE), and the corrosion potential of the steel conductor was -0.306V (vs. SHE). The electrochemical corrosion parameters of the copper / steel grounding electrode in clay (pH=7) are shown in Table 1.

[0126] Step 2: A converter station is planned to be built adjacent to an existing substation. The horizontal distance between the grounding grids of the two substations is 7.6m, and the vertical distance is 10m. The substation grounding grid is... The proposed converter station will use steel conductors. The copper conductors are used. To facilitate GIS grounding and reduce grounding resistance, the grounding grids of the two power stations are connected by an above-ground tie line.

[0127] Using common method-of-moments (MOM) calculation software (such as CDEGS), based on the power station grounding grid design drawing and grounding electrode dimensions, construct the underground grounding device as follows: Figure 9 And at all dissimilar metal conductor connection points (in this case, all copper-steel connection points on the ground tie lines), according to Figure 5b A constant voltage source with a voltage magnitude equal to the corrosion potential is set, and the surface resistivity of the coating layer on all grounding conductors is set to the value of the polarization resistance. The resistivity of the grounding conductor is set to a very small value (1e-15Ω·m in this case), and a corresponding layered soil model is set according to the soil resistivity test results. Then, the method of moments calculation software can automatically generate the linear equation system (14) and complete the calculation to obtain the current density distribution of each conductor in the grounding system.

[0128] Step 3, respectively in R p =0 and R p When ≠0, calculate the distribution of galvanic corrosion current density (spreading current density) on the steel grounding grid, and the results are as follows. Figure 10a and 10b The calculation results for the maximum corrosion current density, maximum overpotential, and total corrosion current flowing through the tie line are shown in Table 3.

[0129] Table 3 Calculation results of galvanic corrosion current

[0130]

[0131] Step 4: Based on the calculation results in Table 3, the applicability of the simplified model is determined according to Equations (12) and (13), as shown in Table 4.

[0132] Table 4. Validity Test of Simplified Model

[0133]

[0134] Table 4 shows that the galvanic corrosion current density and overpotential are sufficiently small to satisfy equation (12) well, therefore R can be used. p The simplified model calculation results when ≠0 are used to obtain the galvanic corrosion rate distribution after the copper / steel grounding grid is connected.

[0135] Step 5, according to Figure 10b Using equation (15), the distribution of the increased corrosion rate due to galvanic corrosion on the steel grounding grid conductor can be calculated as follows: Figure 11 As shown. Among them, by Figure 10b The maximum corrosion current density is 9.111 mA / m. 2 The maximum galvanic corrosion rate is v = 55.845 g × 9.111 mA / m 2 / (2×26.8A·h)=83.16g / m 2 ·a, by Figure 11 It can be seen that the maximum rate of reduction in the diameter of the steel grounding conductor due to galvanic corrosion is 0.0212 mm / a.

[0136] Example 2

[0137] Reference Figure 12 A simplified calculation device for galvanic corrosion rate in a large-scale complex grounding system, comprising:

[0138] Input module: Used to input soil resistivity and electrochemical corrosion parameters;

[0139] Corrosion current density calculation module: used to calculate corrosion current density based on soil resistivity and electrochemical corrosion parameters;

[0140] Galvanic corrosion rate distribution calculation module: used to calculate the galvanic corrosion rate distribution based on corrosion current density.

[0141] Example 3

[0142] This invention provides a computer device, such as... Figure 13 As shown, a device includes a memory and a processor electrically connected together. The memory stores a computer program that can run on the processor. When the processor executes the computer program, it implements the steps of the data processing method described above. For example... Figure 1The steps shown. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the above-described device embodiments.

[0143] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.

[0144] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0145] The memory can be used to store the computer program and / or modules. The processor realizes various functions of the simplified calculation device for galvanic corrosion rate of large-scale complex grounding systems by running or executing the computer program and / or modules stored in the memory and calling the data stored in the memory.

[0146] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0147] Example 4

[0148] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0149] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A simplified calculation method for galvanic corrosion rate in a large-scale complex grounding system, characterized in that, Includes the following steps: S1. Based on the method of moments and the principle of electrochemical corrosion, each grounding body in a large-scale complex grounding system is divided into conductor segments, and the mathematical relationship between the potential and the current of each grounding conductor segment is constructed. At the same time, the mathematical relationship between the node potential and the current of each node in each conductor segment is constructed using the node voltage method. Then, based on the mathematical relationship between the potential of each conductor segment and the node potential of the conductor segment, as well as the relationship between the current of each conductor segment and the current of each node in the conductor segment, a calculation model for galvanic corrosion of a large-scale complex grounding system is obtained. S2. The calculation model of galvanic corrosion of a large-scale complex grounding system is linearized and approximated to obtain a set of linear equations for calculating the current dissipation of each grounding conductor segment. The set of equations is used as the linear equations for calculating the total corrosion current of each grounding conductor segment. The potential drop on the grounding conductor is ignored. The problem of calculating the galvanic corrosion current density is transformed into the problem of calculating the current dissipation of the grounding system under the action of a constant voltage source, so as to realize the calculation of the total corrosion current of each grounding conductor segment. S3. Calculate the corresponding corrosion current density using the total corrosion current of each grounding conductor segment, and calculate the corrosion rate of each grounding conductor segment based on Faraday's law to obtain the galvanic corrosion rate distribution of the entire grounding system. Then, verify the effectiveness of the linearization approximation based on the corrosion current density calculation results: when the approximation conditions are met, the corrosion rate calculation result is the actual corrosion rate of the grounding system; otherwise, the calculation result is only the upper and lower limits of the actual corrosion rate.

2. The simplified calculation method for galvanic corrosion rate in a large-scale complex grounding system according to claim 1, characterized in that, In S1, the calculation model for galvanic corrosion is as follows: (8a) (8b) In the above formula, For overpotential of each grounding conductor segment The vector formed; The corrosion potential of each grounding conductor section The vector formed; M 1 represents the number of conductor segments directly buried in the soil; M 2 represents the number of conductor segments with anti-corrosion coating or exposed to air; K A matrix representing the connection relationship between conductor segments and their endpoints; I j For conductor segment j The scattered current; I For the current to be dispersed by the conductor segment I j The vector formed; The number of rows is M 1 + M 2. A matrix with 1 column and all elements being 1; u 0 represents the node potential of node 1; E 0 represents the absolute electrode potential of the standard hydrogen electrode; B, C , R Z This is a 4-block matrix introduced for ease of writing, and its expression is as follows: , , In the above formula, P It is the identity matrix; L A matrix whose elements are all zero; N The number of nodes; A It is a non-augmented form of the incidence matrix; Y Here are the admittance matrices for each conductor segment; R mj ] represents a matrix composed of mutual resistances, and the first... m Line 1 j The elements of the column are R mj ; P, L and[ R mj The two subscripts represent the row number and column number, respectively. It is a matrix with M1 rows and M2 columns, all of which are zero.

3. The simplified calculation method for galvanic corrosion rate in a large-scale complex grounding system according to claim 1, characterized in that, In S2, the Taylor formula is used to linearize the calculation model of galvanic corrosion in a large-scale complex grounding system.

4. A simplified calculation method for galvanic corrosion rate in a large-scale complex grounding system according to claim 1, characterized in that, In S2, the linear equations for calculating the total corrosion current of each grounded conductor segment are as follows: (14) in, As an intermediate variable; The number of rows is M 1 +M 2. A matrix with 1 column and all elements being 1; For a row with 1 row and a column with 1 column. M 1 +M 2. A matrix whose elements are all 1s; M 1 represents the number of conductor segments directly buried in the soil; M 2 represents the number of conductor segments coated with insulation and exposed to air; I For the current to be dispersed by the conductor segment I j The vector formed; E 0 represents the absolute electrode potential of the standard hydrogen electrode; u 0 represents the node potential of node 1; The corrosion potential of each grounding conductor section The vector formed; The number of rows is M A 2+1 matrix with 1 column and all elements being 0; ， in, P It is the identity matrix; L A matrix whose elements are all zero; P, L and[ R mj The two subscripts represent the row number and column number, respectively. It is a matrix with M1 rows and M2 columns, all of which are zero.

5. A simplified calculation method for galvanic corrosion rate in a large-scale complex grounding system according to claim 1, characterized in that, In S3, the approximate condition is: (12) in, η j For conductor segment j overpotential, β 1 and β 2 represents the Tafel slopes of the anode and cathode, respectively; i L The limiting diffusion current density; S j For the first j Surface area of ​​the conductor segment; i j For the first j Galvanic corrosion current density on the conductor segment; I j For conductor segment j The scattered current.

6. A simplified calculation method for galvanic corrosion rate in a large-scale complex grounding system according to claim 1, characterized in that, In S3, the formula for calculating the corrosion rate of each grounding conductor segment is as follows: (15) in, I j For conductor segment j The scattered current; S j For the first j Surface area of ​​the conductor segment; n It is the equivalent of an electrochemical reaction; F It is Faraday's constant; A The molar mass of the corroded material; v j For the first j Average corrosion rate on conductor segment, g / (m 2. h).

7. The simplified calculation method for galvanic corrosion rate in a large-scale complex grounding system according to claim 1, characterized in that, In step S3, when the simplification condition is not met, the polarization resistance is used as a reference. R p When the total corrosion current of each grounding conductor segment is not equal to 0, the total corrosion current of each grounding conductor segment is calculated using a linear equation system. Based on this total corrosion current, the lower limit of the corrosion rate increase due to galvanic corrosion in the grounding system is calculated. This is based on the polarization resistance. R p When =0, the total corrosion current of each grounding conductor segment is calculated by the linear equation system of the total corrosion current of each grounding conductor segment, and the upper limit of the corrosion rate increase of the grounding system due to galvanic corrosion is calculated based on the total corrosion current of each grounding conductor segment.

8. A simplified calculation device for galvanic corrosion rate in a large-scale complex grounding system, used to implement the method of claim 1, characterized in that, include: Input module: Used to input soil resistivity and electrochemical corrosion parameters; Corrosion current density calculation module: used to calculate corrosion current density based on soil resistivity and electrochemical corrosion parameters; Galvanic corrosion rate distribution calculation module: used to calculate the galvanic corrosion rate distribution based on corrosion current density.

9. A computer device, characterized in that, The method includes an electrically connected memory and a processor, wherein the memory stores a computer program that can run on the processor, and when the processor executes the computer program, it implements the steps of the method according to any one of claims 1-7.

Images