A method and system for evaluating impedance of a grounding conductor considering cross-section corrosion morphology

Abstract

The application discloses a grounding conductor impedance evaluation method and system considering section corrosion morphology, relates to the technical field of grounding conductor impedance evaluation of a power system, and comprises the following steps: acquiring physical parameters of a grounding conductor and an electron microscope scanning graph of a corrosion section of the grounding conductor; establishing a grounding conductor section electromagnetic field mathematical model according to the physical parameters of the grounding conductor, and combining a ferromagnetic characteristic curve of the grounding conductor to establish a grounding conductor conduction impedance evaluation equation; performing finite element grid dissection on the electron microscope scanning graph of the corrosion section of the grounding conductor to obtain a finite element grid graph; iteratively solving the grounding conductor conduction impedance evaluation equation by using the finite element grid graph to obtain a current density and an electric field intensity of the corrosion section of the grounding conductor; finally, the unit length conduction impedance of the grounding conductor is calculated to complete the grounding conductor conduction impedance evaluation. The application can accurately calculate the conduction impedance of the grounding conductor with different section corrosion morphologies, and provides a reference for grounding net corrosion diagnosis.

Description

Technical Field

[0001] This invention relates to the technical field of power system grounding conductor measurement and evaluation, and more specifically, to a method and system for evaluating grounding conductor impedance considering cross-sectional corrosion morphology. Background Technology

[0002] Grounding devices are crucial for power system safety, but they are susceptible to corrosion. The corrosive environment of grounding devices is mainly divided into atmospheric corrosion and soil corrosion. Grounding down conductors and grounding electrodes in cable trenches are prone to atmospheric corrosion, while various vertical and horizontal grounding electrodes are prone to soil corrosion. Grounding devices are buried underground in a harsh operating environment, and the parts most susceptible to corrosion include: ① equipment grounding down conductors and their connecting screws; ② all welded joints; ③ equipotential bonding strips in cable trenches; ④ horizontal grounding electrodes. These locations represent typical positions of grounding devices, subject to both atmospheric and soil corrosion. Overall, the main factor causing corrosion is electrochemical corrosion. Currently, diagnostic methods for grounding grid corrosion can be divided into electrical, magnetic, and electrochemical methods. In corrosion assessment, in addition to classic comparative methods, topology detection methods, and traditional optimization methods, artificial intelligence and image recognition have been widely applied. These new methods have achieved good results, but they have also raised a new problem—how to evaluate the grounding characteristics of the grounding grid under different corrosion conditions. In reality, the corrosion depth on the metal surface of buried grounding conductors is uneven. If, through macroscopic observation, the corrosion depth in a localized area is significantly greater than that in adjacent areas, it is considered localized corrosion. After a period of operation in the soil environment, corrosion pits or pitting may appear on the metal surface of buried grounding conductors. Over time, these pits deepen, forming small pitted corrosion pits. This type of corrosion is called pitting corrosion, or simply pitting corrosion. Figure 1 As shown, common pitting corrosion morphologies include 1-a narrow and deep, 1-b elliptical, 1-c wide and shallow, 1-d subcutaneous, 1-e undercut, 1-f horizontal, and 1-g vertical. Most pits are small and deep, with a diameter generally less than 2 mm, and the depth often exceeds the diameter, sometimes even penetrating buried grounding conductors. Pits are scattered or densely distributed on the metal surface, with most openings covered by corrosion products, while a few are open and uncovered. Therefore, pitting corrosion is a type of localized corrosion that is concealed in appearance but highly destructive. Existing techniques analyze corrosion effects based on equivalent cross-sectional area, resulting in inaccurate assessments. Therefore, an impedance assessment method that considers the influence of corrosion morphology on the grounding conductor cross-section is urgently needed.

[0003] Existing technology discloses a high-frequency equipotential bonding impedance measurement method, belonging to the field of lightning protection equipotential bonding technology. This application generates a 1Hz-1MHz test current flowing through the grounding electrode, obtains the effective voltage and current values, and then calculates the resistance, impedance, and inductance based on the test current at different frequencies. It then evaluates the grounding electrode by comprehensively considering the grounding electrode impedance evaluation value, historical measurement data of qualified grounding electrodes, and historical impedance curves. This invention simulates lightning current using a high-frequency sinusoidal test current to detect whether there are problems with the grounding electrode. Without affecting normal use, it measures the impedance and uses inductance as the basis for evaluating the quality and corrosion degree of the grounding electrode. However, this application does not consider the actual cross-sectional corrosion morphology of the grounding electrode, analyzing the corrosion effect based on equivalent cross-sectional area, and cannot accurately calculate the conduction impedance of the grounding conductor with different cross-sectional corrosion morphologies. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies that do not consider cross-sectional corrosion morphology when assessing the impedance of grounding conductors, this invention provides a method and system for assessing the impedance of grounding conductors that takes into account cross-sectional corrosion morphology. This method and system can accurately calculate the conduction impedance of grounding conductors with different cross-sectional corrosion morphologies, providing a reference for the diagnosis of grounding grid corrosion.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] This invention discloses a method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology, comprising:

[0007] S1: Obtain the physical parameters of the grounding conductor and its corrosion cross-section using an electron microscope;

[0008] S2: Establish a mathematical model of the electromagnetic field of the grounding conductor cross-section based on the physical parameters of the grounding conductor;

[0009] S3: Obtain the ferromagnetic characteristic curve of the grounding conductor, and combine the data of the ferromagnetic characteristic curve with the electromagnetic field mathematical model of the grounding conductor cross section to establish the grounding conductor conduction impedance evaluation equation;

[0010] S4: Finite element mesh generation is performed on the electron microscope scan image of the corroded cross section of the grounding conductor to obtain the finite element mesh image;

[0011] S5: Based on the finite element mesh diagram, the equation for evaluating the conduction impedance of the grounding conductor is solved iteratively to obtain the current density and electric field intensity of the corroded cross section of the grounding conductor;

[0012] S6: Calculate the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section of the grounding conductor, and complete the assessment of the conduction impedance of the grounding conductor.

[0013] Preferably, the physical parameters of the grounding conductor include resistivity, perimeter, and corrosion cross-sectional area.

[0014] Preferably, in step S2, the specific method for establishing the electromagnetic field mathematical model of the grounded conductor cross-section is as follows:

[0015] Let the magnetic field strength within the cross-section of the grounded conductor be H, the electric field strength be E, and the current density be J. Establish Maxwell's equations for the grounded conductor:

[0016]

[0017]

[0018] In the formula, Let x and y represent the x and y coordinates of the electromagnetic field point, t represent time, ρ represent the resistivity of the grounded conductor, B represent the magnetic flux density, and μ0 represent the permeability of free space. Assuming JEBH is a sine wave with angular frequency ω, the above Maxwell's equations can be rewritten as:

[0019]

[0020]

[0021] Introducing the magnetic potential column vector A, the above system of equations is equivalent to:

[0022]

[0023] Rewriting the above equation in functional form, we can use it as an expression for the mathematical model of the electromagnetic field of a grounded conductor cross section:

[0024]

[0025] In the formula, j represents the imaginary unit.

[0026] Preferably, the specific method of step S3 is as follows:

[0027] Based on the nonlinear magnetization characteristics of the grounding conductor, the relative permeability of the grounding conductor is set as follows:

[0028]

[0029] In the formula, μ r Represents the relative permeability of a grounded conductor;

[0030] The ferromagnetic characteristic curve of a grounding conductor is the relationship curve between the relative permeability and the magnetic field strength of the grounding conductor. By substituting the data from the ferromagnetic characteristic curve into the expression of the electromagnetic field mathematical model of the grounding conductor cross section, the conduction impedance evaluation equation of the grounding conductor is obtained.

[0031] Preferably, in step S4, the specific method for performing finite element mesh generation on the electron microscope scan image of the corroded cross-section of the grounding conductor to obtain the finite element mesh image is as follows:

[0032] A minimum mesh size is set, and the electron microscope scan image of the corrosion section of the grounding conductor is meshed using a triangular face mesh. Each triangular mesh element and its vertex are numbered to obtain the finite element mesh.

[0033] Preferably, in step S5, the specific method for iteratively solving the grounding conductor conduction impedance evaluation equation based on the finite element mesh diagram to obtain the current density and electric field strength of the grounding conductor corrosion cross section is as follows:

[0034] S5.1: Based on the finite element mesh diagram, establish the finite element equation for the evaluation equation of the conduction impedance of the grounding conductor;

[0035] S5.2: Set the iteration count q and initialize the parameters by setting q = 0.

[0036] S5.3: Calculate the q-round vector magnetic position column vector A (q) And the magnetic induction intensity B of the qth cycle (q) ;

[0037] S5.4: Based on the magnetic induction intensity B in cycle q (q) Calculate the magnetic field strength H in round (q+1). (q+1) The magnetization M in round (q+1) (q+1) ;

[0038] S5.5: Obtain the magnetic field strength H of the (q+1)th cycle from the ferromagnetic characteristic curve of the grounded conductor. (q+1) The corresponding (q+1)-th order relative permeability The electric field strength E in round (q+1) was calculated based on Maxwell's equations. (q+1) ;

[0039] S5.6: Magnetic induction intensity B (q) Magnetic field strength H (q+1) Magnetization M (q+1) and electric field strength E (q+1) Substituting into the finite element equation, calculate the vector magnetic potential column vector A for cycle (q+1). (q+1) ;

[0040] S5.7: Calculate the vector magnetic position column vector A (q+1) and A (q) The difference is used to determine whether it is less than the preset iteration error. If not, proceed to step S5.8; otherwise, proceed to step S5.9.

[0041] S5.8: Let the iteration number q = q + 1, and repeat steps S5.3-S5.7;

[0042] S5.9: The electric field strength E in round (q+1) (q+1) Substituting into Maxwell's equations to calculate the current density, the electric field strength E... (q+1) The electric field strength E, which is the corroded cross section of the grounding conductor, is output together with the current density J.

[0043] Preferably, in step S5.1, the finite element equation established based on the finite element mesh diagram for evaluating the conduction impedance of the grounding conductor is specifically as follows:

[0044] KA+jTA=P

[0045] Where K and T represent the first and second node coefficient matrices of the finite element mesh, respectively, P represents the nodal excitation current column vector of the finite element mesh, A represents the vector magnetic potential column vector, and j represents the imaginary unit;

[0046] For a triangular mesh cell k, the three vertices are i, j, and m, and the vertex coordinates are (x, j, m) and (x, j, m). i y i ), (x j y j ), (x m y m );

[0047] Then the non-zero elements of the coefficient matrix K of the first node are:

[0048]

[0049]

[0050]

[0051] Where, Δ k Δ represents the area of ​​triangular mesh cell k. k =0.5(b) i c j -b j c i );b i b j b m c i c j c m All are intermediate quantities, b i =y j -y m b j =y m -y i b m =y i -y j c i =x j-x m c j =x m -x i c m =x i -x j ;

[0052] The non-zero elements of the second node coefficient matrix T are:

[0053]

[0054] Where, δ ij Denotes the first parameter, δ when i = j. ij =1, otherwise δ ij =0;

[0055]

[0056] In the formula, P k This represents the column vector of nodal excitation currents for finite element mesh element k.

[0057] Preferably, in step S5.3, the vector magnetic position column vector A of the q-round sequence is calculated. (q) And the magnetic induction intensity B of the qth cycle (q) The specific method is as follows:

[0058]

[0059]

[0060] In the formula, I represents the phasor current flowing through the grounding conductor, and S represents the corroded cross-sectional area of ​​the grounding conductor.

[0061] Preferably, in step S5.4, the magnetic induction intensity B is determined according to the q-th cycle. (q) Calculate the magnetic field strength H in round (q+1). (q +1) The magnetization M in round (q+1) (q+1) :

[0062]

[0063]

[0064] In the formula, μ0 represents the vacuum permeability.

[0065] Preferably, in step S5.5, the electric field strength E for round (q+1) is calculated based on Maxwell's equations. (q +1) The specific method is as follows:

[0066] E (q+1)(x, y) = ρΔ × H (q+1)

[0067] Preferably, the specific method of step S5.7 is as follows:

[0068] Let the preset iteration error be ε, and compare ε with |A|. (q+1) -A (q) The size of |; if |A (q+1) -A (q) If | < ε, proceed to step S5.9; otherwise, proceed to the next iteration.

[0069] Preferably, in step S5.9, the electric field intensity E of round (q+1) is... (q+1) The specific method for calculating the current density J by substituting into Maxwell's equations is as follows:

[0070]

[0071] Preferably, in step S6, the specific method for calculating the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section of the grounding conductor is as follows:

[0072]

[0073] In the formula, Z c The impedance per unit length of the grounding conductor is represented by L, where L represents the perimeter of the grounding conductor; l represents the integration path, which is the outer surface of the grounding conductor.

[0074] This invention also provides a grounding conductor impedance assessment system that considers cross-sectional corrosion morphology, and the method for implementing the above-mentioned grounding conductor impedance assessment method considering cross-sectional corrosion morphology includes:

[0075] The data acquisition module is used to acquire the physical parameters of the grounding conductor and the electron microscope scan image of its corrosion cross section;

[0076] The model building module is used to build a mathematical model of the electromagnetic field of the grounding conductor cross section based on the physical parameters of the grounding conductor.

[0077] The evaluation equation establishment module is used to obtain the ferromagnetic characteristic curve of the grounding conductor, and combine the data of the ferromagnetic characteristic curve with the electromagnetic field mathematical model of the grounding conductor cross section to establish the evaluation equation of the grounding conductor conduction impedance.

[0078] The finite element meshing module is used to perform finite element mesh generation on the electron microscope scan image of the corrosion section of the grounding conductor to obtain a finite element mesh image;

[0079] The finite element solution module is used to iteratively solve the grounding conductor conduction impedance evaluation equation based on the finite element mesh diagram, and obtain the current density and electric field intensity of the grounding conductor corrosion section;

[0080] The impedance assessment module is used to calculate the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section, and to complete the conduction impedance assessment of the grounding conductor.

[0081] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0082] This application first obtains the physical parameters of the grounding conductor and the actual scanning electron microscope (SEM) image of the corrosion cross section. Using the physical parameters of the grounding conductor, a mathematical model of the electromagnetic field of the cross section is established. Considering the ferromagnetic properties of the grounding conductor, an evaluation equation for the conduction impedance of the grounding conductor is established. The SEM image of the corrosion cross section reflects the actual corrosion morphology of the grounding conductor. Furthermore, a finite element mesh diagram is constructed based on the actual corrosion morphology. The conduction impedance of the grounding conductor is accurately solved based on the finite element mesh diagram, obtaining the distribution law of current density and electric field intensity of the grounding conductor under the corrosion morphology. Finally, the conduction impedance per unit length of the grounding conductor is quantitatively calculated and compared with the conduction impedance per unit length when the grounding conductor is not corroded. The influence of different cross-sectional corrosion morphologies on the conduction impedance of the grounding conductor is accurately analyzed. The analysis results are consistent with reality and can provide a strong reference for the corrosion diagnosis of grounding grids. Attached Figure Description

[0083] Figure 1 This is a schematic diagram of the common pitting morphology of grounding conductors described in the background art.

[0084] Figure 2 This is a flowchart of a grounding conductor impedance evaluation method considering cross-sectional corrosion morphology as described in Example 1.

[0085] Figure 3 This is a schematic diagram of the ferromagnetic characteristic curve of the steel conductor described in Example 2.

[0086] Figure 4 This is a schematic diagram of the triangular mesh unit described in Example 2.

[0087] Figure 5 This is a schematic diagram of the finite element mesh of the narrow and deep corrosion morphology described in Example 2.

[0088] Figure 6 This is a schematic diagram of the current density distribution of the grounding conductor described in Example 2.

[0089] Figure 7 This is a schematic diagram of the electric field intensity distribution of the grounding conductor described in Example 2.

[0090] Figure 8 This is a schematic diagram of the relative permeability distribution of the grounding conductor described in Example 2.

[0091] Figure 9This is a schematic diagram of the structure of a grounding conductor impedance evaluation system that considers cross-sectional corrosion morphology, as described in Example 3. Detailed Implementation

[0092] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0093] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions;

[0094] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0095] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0096] Example 1

[0097] This embodiment discloses a method for evaluating the impedance of a grounding conductor that considers the cross-sectional corrosion morphology, such as... Figure 2 As shown, it includes:

[0098] S1: Obtain the physical parameters of the grounding conductor and its corrosion cross-section using an electron microscope;

[0099] S2: Establish a mathematical model of the electromagnetic field of the grounding conductor cross-section based on the physical parameters of the grounding conductor;

[0100] S3: Obtain the ferromagnetic characteristic curve of the grounding conductor, and combine the data of the ferromagnetic characteristic curve with the electromagnetic field mathematical model of the grounding conductor cross section to establish the grounding conductor conduction impedance evaluation equation;

[0101] S4: Finite element mesh generation is performed on the electron microscope scan image of the corroded cross section of the grounding conductor to obtain the finite element mesh image;

[0102] S5: Based on the finite element mesh diagram, the equation for evaluating the conduction impedance of the grounding conductor is solved iteratively to obtain the current density and electric field intensity of the corroded cross section of the grounding conductor;

[0103] S6: Calculate the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section of the grounding conductor, and complete the assessment of the conduction impedance of the grounding conductor.

[0104] In the specific implementation process, this embodiment first obtains the physical parameters of the grounding conductor and the actual scanning electron microscope (SEM) image of the corrosion cross section. Using the physical parameters of the grounding conductor, a mathematical model of the electromagnetic field of the cross section is established. Considering the ferromagnetic properties of the grounding conductor, an evaluation equation for the grounding conductor's conduction impedance is established. The SEM image of the corrosion cross section reflects the actual corrosion morphology of the grounding conductor. Furthermore, a finite element mesh diagram is constructed based on the actual corrosion morphology. The conduction impedance of the grounding conductor is accurately solved based on the finite element mesh diagram, obtaining the distribution law of current density and electric field intensity of the grounding conductor under the cross section corrosion morphology. Finally, the conduction impedance per unit length of the grounding conductor is calculated and compared with the conduction impedance per unit length when the grounding conductor is not corroded. The influence of different cross section corrosion morphologies on the conduction impedance of the grounding conductor is accurately analyzed. The analysis results are consistent with reality and can provide a strong reference for the corrosion diagnosis of the grounding grid.

[0105] Example 2

[0106] This embodiment discloses a method for evaluating the impedance of a grounding conductor that considers the cross-sectional corrosion morphology, including:

[0107] S1: Obtain the physical parameters of the grounding conductor and its corrosion cross-section using an electron microscope; the physical parameters of the grounding conductor include resistivity, perimeter, and corrosion cross-sectional area;

[0108] S2: Establish a mathematical model of the electromagnetic field of the grounding conductor cross-section based on the physical parameters of the grounding conductor; specifically:

[0109] Let the magnetic field strength within the cross-section of the grounded conductor be H, the electric field strength be E, and the current density be J. Establish Maxwell's equations for the grounded conductor:

[0110]

[0111]

[0112] In the formula, Let x and y represent the x and y coordinates of the electromagnetic field point, t represent time, ρ represent the resistivity of the grounded conductor, B represent the magnetic flux density, and μ0 represent the permeability of free space. Assuming JEBH is a sine wave with angular frequency ω, the above Maxwell's equations can be rewritten as:

[0113]

[0114]

[0115] Introducing the magnetic potential column vector A, the problems described by formulas (1) to (4) are equivalent to:

[0116]

[0117] Rewriting the above equation in functional form, we can use it as an expression for the mathematical model of the electromagnetic field of a grounded conductor cross section:

[0118]

[0119] In the formula, j represents the imaginary unit.

[0120] S3: Obtain the ferromagnetic characteristic curve of the grounding conductor, and combine the data of the ferromagnetic characteristic curve with the electromagnetic field mathematical model of the grounding conductor cross section to establish the grounding conductor conduction impedance evaluation equation;

[0121] In this embodiment, the grounding conductor is made of steel, which is a nonlinear electrical material. Considering the nonlinear magnetization characteristics of steel, the relative permeability of the grounding conductor is set as follows:

[0122]

[0123] In the formula, μ r Represents the relative permeability of a grounded conductor;

[0124] The ferromagnetic characteristic curve of a grounded conductor is the relationship curve between the relative permeability and the magnetic field strength of the grounded conductor, such as... Figure 3 As shown, the ferromagnetic characteristic curve of the steel conductor in this embodiment is obtained by substituting the data of the ferromagnetic characteristic curve into the expression of the electromagnetic field mathematical model of the grounding conductor cross section.

[0125] S4: Finite element mesh generation is performed on the electron microscope scan image of the corroded cross section of the grounding conductor to obtain the finite element mesh image;

[0126] A minimum mesh size is set, and a triangular mesh is used to mesh the electron microscope scan image of the corroded cross-section of the grounding conductor. Each triangular mesh cell and its vertices are numbered, such as... Figure 4 As shown, k is the number of the triangular mesh element, and the three vertices are numbered i, j, and m, respectively. This embodiment uses an electron microscope scan of a narrow, deep corrosion morphology as an example. The minimum mesh size is set to 0.02 mm. After meshing, the obtained finite element mesh is shown below. Figure 5 As shown.

[0127] S5: Based on the finite element mesh diagram, the equation for evaluating the conduction impedance of the grounding conductor is solved iteratively to obtain the current density and electric field intensity of the corroded cross section of the grounding conductor; specifically:

[0128] S5.1: Based on the finite element mesh diagram, establish the finite element equation for the evaluation equation of the conduction impedance of the grounding conductor;

[0129] KA+jTA=P (8)

[0130] Where K and T represent the first and second node coefficient matrices of the finite element mesh, respectively, P represents the nodal excitation current column vector of the finite element mesh, A represents the vector magnetic potential column vector, and j represents the imaginary unit;

[0131] For a triangular mesh cell k, the three vertices are i, j, and m, and the vertex coordinates are (x, j, m) and (x, j, m). i y i ), (x j y j ), (x m y m );

[0132] Then the non-zero elements of the coefficient matrix K of the first node are:

[0133]

[0134]

[0135]

[0136] Where, Δ k Δ represents the area of ​​triangular mesh cell k. k =0.5(b) i c j -b j c i );b i b j b m c i c j c m All are intermediate quantities, b i =y j -y m b j =y m -y i b m =y i -y j c i =x j -x m c j =x m -x i c m =x i -x j ;

[0137] The non-zero elements of the second node coefficient matrix T are:

[0138]

[0139] Where, δij Denotes the first parameter, δ when i = j. ij =1, otherwise δ ij =0;

[0140] The column vector of nodal excitation currents in the finite element mesh is:

[0141]

[0142] In the formula, P k This represents the column vector of nodal excitation currents of finite element mesh element k;

[0143] S5.2: Set the iteration count q and initialize the parameters by setting q = 0.

[0144] S5.3: Calculate the q-round vector magnetic position column vector A (q) And the magnetic induction intensity B of the qth cycle (q) ;

[0145]

[0146]

[0147] In the formula, I represents the phasor current flowing through the grounding conductor, and S represents the cross-sectional area of ​​corrosion of the grounding conductor, calculated based on the uniform distribution of I across the cross-sectional area of ​​corrosion of the grounding conductor.

[0148] S5.4: Based on the magnetic induction intensity B in cycle q (q) Calculate the magnetic field strength H in round (q+1). (q+1) The magnetization M in round (q+1) (q+1) ;

[0149]

[0150]

[0151] S5.5: Obtain the magnetic field strength H of the (q+1)th cycle from the ferromagnetic characteristic curve of the grounded conductor. (q+1) The corresponding (q+1)-th order relative permeability The electric field strength E in round (q+1) was calculated based on Maxwell's equations. (q+1) ;

[0152] Update the magnetic field strength, in Figure 2 The magnetic field strength H is obtained from the middle (q+1 The relative permeability of the (q+1)th cycle corresponding to ) The electric field strength E for round (q+1) is calculated according to equation (3). (q+1) :

[0153]

[0154] S5.6: Magnetic induction intensity b (q) Magnetic field strength H (q+1) Magnetization M (q+1) and electric field strength E (q+1) Substituting into the finite element equation, calculate the vector magnetic potential column vector A for cycle (q+1). (q+1) ;

[0155] S5.7: Calculate the vector magnetic position column vector A (q+1) and A (q) The difference is used to determine whether it is less than the preset iteration error. If not, proceed to step S5.8; otherwise, proceed to step S5.9.

[0156] Let the preset iteration error be ε, and compare ε with |A|. (q+1) -A (q) The size of |; if |A (q+1) -A (q) If | < ε, proceed to step S5.9; otherwise, execute step S5.8 for the next iteration. In this embodiment, the preset iteration error ε is 10. -12 Wb / m;

[0157] S5.8: Let the iteration number q = q + 1, and repeat steps S5.3-S5.7;

[0158] Substituting equations (15) to (18) into equation (8) updates A. Then, substituting the updated A back into equations (15) to (18) performs the next round of judgment until |A| is reached. (q+1) -A (q) |<ε;

[0159] S5.9: The electric field strength E in round (q+1) (q+1) Substituting into Maxwell's equations to calculate the current density, the electric field strength E... (q+1) The electric field strength E, which is the corroded cross section of the grounding conductor, is output together with the current density J.

[0160] The electric field strength E (q+1) Substituting into equation (3), the current density J is calculated:

[0161]

[0162] S6: Calculate the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section of the grounding conductor, and complete the assessment of the conduction impedance of the grounding conductor.

[0163]

[0164] In the formula, Z cThe impedance per unit length of the grounding conductor is represented by L, where L represents the perimeter of the grounding conductor; l represents the integration path, which is the outer surface of the grounding conductor.

[0165] In this embodiment, as Figure 6 , 7 Figures 8 and 9 show schematic diagrams of the current density distribution, electric field intensity distribution, and relative permeability distribution of a grounding conductor, respectively. The calculated on-resistance Z per unit length of the grounding conductor with narrow, deep cross-section corrosion morphology is also shown. c The impedance is 3.41 + j3.35 mΩ, which is significantly lower than the 5.91 + j5.46 mΩ per unit length when the grounding conductor is uncorroded. Furthermore, considering... Figures 5-7 The distribution diagram shows that changes in conduction impedance alter the grounding performance of the grounding grid and can also assist in the diagnosis of grounding grid corrosion.

[0166] This embodiment presents a grounding conductor impedance assessment method considering cross-sectional corrosion morphology, which can analyze the impact of different morphologies of localized corrosion on the grounding conductivity of steel grounding electrodes. The method considers the nonlinear magnetic properties of the conductor and can perform two-dimensional finite element modeling and calculation of grounding current flow on the conductor cross-section by combining different pitting morphologies. In application, it can specifically analyze the cross-sectional current density, magnetization characteristics, electric field, and magnetic field distribution patterns corresponding to different corrosion morphologies and current magnitudes for round steel and flat steel, achieving the goal of quantitatively analyzing the influence of different pitting morphologies on the unit length conduction impedance. This method overcomes the shortcomings of previous methods that approximate the corrosion effect based on equivalent cross-sectional area, providing an effective means to assess the impact of non-uniform corrosion on the current flow characteristics of grounding conductors.

[0167] Example 3

[0168] This embodiment provides a grounding conductor impedance assessment system that considers cross-sectional corrosion morphology, such as... Figure 9 As shown, the system for implementing the grounding conductor impedance assessment method considering cross-sectional corrosion morphology as described in Embodiment 1 or 2 includes:

[0169] The data acquisition module is used to acquire the physical parameters of the grounding conductor and the electron microscope scan image of its corrosion cross section;

[0170] The model building module is used to build a mathematical model of the electromagnetic field of the grounding conductor cross section based on the physical parameters of the grounding conductor.

[0171] The evaluation equation establishment module is used to obtain the ferromagnetic characteristic curve of the grounding conductor, and combine the data of the ferromagnetic characteristic curve with the electromagnetic field mathematical model of the grounding conductor cross section to establish the evaluation equation of the grounding conductor conduction impedance.

[0172] The finite element meshing module is used to perform finite element mesh generation on the electron microscope scan image of the corrosion section of the grounding conductor to obtain a finite element mesh image;

[0173] The finite element solution module is used to iteratively solve the grounding conductor conduction impedance evaluation equation based on the finite element mesh diagram, and obtain the current density and electric field intensity of the grounding conductor corrosion section;

[0174] The impedance assessment module is used to calculate the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section, and to complete the conduction impedance assessment of the grounding conductor.

[0175] The same or similar labels correspond to the same or similar parts;

[0176] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0177] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology, characterized in that, include: S1: Obtain the physical parameters of the grounding conductor and its corrosion cross-section using an electron microscope; S2: Establish a mathematical model of the electromagnetic field of the grounding conductor cross-section based on the physical parameters of the grounding conductor; S3: Obtain the ferromagnetic characteristic curve of the grounding conductor, and combine the data of the ferromagnetic characteristic curve with the electromagnetic field mathematical model of the grounding conductor cross section to establish the grounding conductor conduction impedance evaluation equation; S4: Finite element mesh generation is performed on the electron microscope scan image of the corroded cross section of the grounding conductor to obtain the finite element mesh image; S5: Based on the finite element mesh diagram, the equation for evaluating the conduction impedance of the grounding conductor is solved iteratively to obtain the current density and electric field intensity of the corroded cross section of the grounding conductor; S6: Calculate the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section of the grounding conductor, and complete the assessment of the conduction impedance of the grounding conductor.

2. The method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology according to claim 1, characterized in that, The physical parameters of the grounding conductor include resistivity, perimeter, and corroded cross-sectional area.

3. The method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology according to claim 2, characterized in that, In step S2, the specific method for establishing the electromagnetic field mathematical model of the grounded conductor cross-section is as follows: Let the magnetic field strength within the cross-section of the grounded conductor be H, the electric field strength be E, and the current density be J. Establish Maxwell's equations for the grounded conductor: In the formula, Let x and y represent the x and y coordinates of the electromagnetic field point, t represent time, ρ represent the resistivity of the grounded conductor, B represent the magnetic flux density, μ0 represent the permeability of free space, and M represent the magnetization. Assuming JEBH is a sine wave with angular frequency ω, the above Maxwell's equations can be rewritten as: Introducing the magnetic potential column vector A, the above system of equations is equivalent to: Rewriting the above equation in functional form, we can use it as an expression for the mathematical model of the electromagnetic field of a grounded conductor cross section: In the formula, j represents the imaginary unit.

4. The method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology according to claim 3, characterized in that, The specific method for step S3 is as follows: Based on the nonlinear magnetization characteristics of the grounding conductor, the relative permeability of the grounding conductor is set as follows: In the formula, μ r Represents the relative permeability of a grounded conductor; The ferromagnetic characteristic curve of a grounding conductor is the relationship curve between the relative permeability and the magnetic field strength of the grounding conductor. By substituting the data from the ferromagnetic characteristic curve into the expression of the electromagnetic field mathematical model of the grounding conductor cross section, the conduction impedance evaluation equation of the grounding conductor is obtained.

5. The method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology according to claim 1, characterized in that, In step S5, the specific method for iteratively solving the grounding conductor conduction impedance evaluation equation based on the finite element mesh diagram to obtain the current density and electric field strength of the grounding conductor corrosion cross section is as follows: S5.1: Based on the finite element mesh diagram, establish the finite element equation for the evaluation equation of the conduction impedance of the grounding conductor; S5.2: Set the iteration count q and initialize the parameters by setting q = 0. S5.3: Calculate the q-round vector magnetic position column vector A (q) And the magnetic induction intensity B of the qth cycle (q) ; S5.4: Based on the magnetic induction intensity B of round q (q) Calculate the magnetic field strength H in round (q+1). (q+1) The magnetization M in round (q+1) (q+1) ; S5.5: Obtain the magnetic field strength H of the (q+1)th cycle from the ferromagnetic characteristic curve of the grounded conductor. (q+1) The corresponding (q+1) round relative permeability The electric field strength E in round (q+1) was calculated based on Maxwell's equations. (q+1) ; S5.6: Magnetic induction intensity B (q) Magnetic field strength H (q+1) Magnetization M (q+1) and electric field strength E (q+1) Substituting into the finite element equation, calculate the vector magnetic potential column vector A for cycle (q+1). (q+1) ; S5.7: Calculate the vector magnetic position column vector A (q+1) and A (q) The difference is used to determine whether it is less than the preset iteration error. If not, proceed to step S5.8; otherwise, proceed to step S5.

9. S5.8: Let the iteration number q = q + 1, and repeat steps S5.3-S5.7; S5.9: The electric field strength E in round (q+1) (q+1) Substituting into Maxwell's equations to calculate the current density J, and then substituting the electric field strength E... (q+1) The electric field strength E, which is the corroded cross section of the grounding conductor, is output together with the current density J.

6. The method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology according to claim 5, characterized in that, In step S5.1, the finite element equation established based on the finite element mesh diagram for evaluating the conduction impedance of the grounding conductor is as follows: KA+jTA=P Where K and T represent the first and second node coefficient matrices of the finite element mesh, respectively, P represents the nodal excitation current column vector of the finite element mesh, A represents the vector magnetic potential column vector, and j represents the imaginary unit; For a triangular mesh cell k, the three vertices are i, j, and m, and the vertex coordinates are (x, j, m). i ,y i ),(x j ,y j ),(x m ,y m ); Then the non-zero elements of the coefficient matrix K of the first node are: Where, Δ k Δ represents the area of ​​triangular mesh cell k. k =0.5(b) i c j -b j c i );b i ,b j ,b m ,c i ,c j ,c m All are intermediate quantities, b i =y j -y m b j =y m -y i b m =y i -y j c i =x j -x m c j =x m -x i c m =x i -x j ; The non-zero elements of the second node coefficient matrix T are: Where, δ ij Denotes the first parameter, δ when i = j. ij =1, otherwise δ ij =0; In the formula, P k This represents the column vector of nodal excitation currents for finite element mesh element k.

7. The method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology according to claim 6, characterized in that, In step S5.3, the magnetic position column vector A of the q-cycle vector is calculated. (q) And the magnetic induction intensity B of the qth cycle (q) The specific method is as follows: In the formula, I represents the phasor current flowing through the grounding conductor, and S represents the cross-sectional area of ​​the grounding conductor under corrosion.

8. The method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology according to claim 7, characterized in that, In step S5.4, based on the magnetic induction intensity B of round q... (q) Calculate the magnetic field strength H in round (q+1). (q+1) The magnetization M in round (q+1) (q+1) : In the formula, μ0 represents the vacuum permeability.

9. The method for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology according to claim 7, characterized in that, In step S6, the specific method for calculating the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section is as follows: In the formula, Z c The impedance per unit length of the grounding conductor is represented by L, where L represents the perimeter of the grounding conductor; l represents the integration path, which is the outer surface of the grounding conductor.

10. A system for evaluating the impedance of a grounding conductor considering cross-sectional corrosion morphology, characterized in that, For implementing the grounding conductor impedance assessment method considering cross-sectional corrosion morphology as described in any one of claims 1-9, the system comprises: The data acquisition module is used to acquire the physical parameters of the grounding conductor and the electron microscope scan image of its corrosion cross section; The model building module is used to build a mathematical model of the electromagnetic field of the grounding conductor cross section based on the physical parameters of the grounding conductor. The evaluation equation establishment module is used to obtain the ferromagnetic characteristic curve of the grounding conductor, and combine the data of the ferromagnetic characteristic curve with the electromagnetic field mathematical model of the grounding conductor cross section to establish the evaluation equation of the grounding conductor conduction impedance. The finite element meshing module is used to perform finite element mesh generation on the electron microscope scan image of the corrosion section of the grounding conductor to obtain a finite element mesh image; The finite element solution module is used to iteratively solve the grounding conductor conduction impedance evaluation equation based on the finite element mesh diagram, and obtain the current density and electric field intensity of the grounding conductor corrosion section; The impedance assessment module is used to calculate the conduction impedance per unit length of the grounding conductor based on the current density and electric field strength of the corroded cross section, and to complete the conduction impedance assessment of the grounding conductor.

Images