Direct current grounding electrode near-zone grounding system local corrosion depth evaluation method and system

Abstract

The application discloses a DC grounding electrode near-zone grounding system local corrosion depth evaluation method and system evaluation method, obtains the total amount of the grounding system ground current according to the simulation calculation result of the DC bias magnetism or the bias current measurement result of the neutral point of the grounding transformer of the substation, establishes the model of the branch and the node of the grounding system, obtains the branch voltage correlation matrix and the branch voltage drop correlation matrix to solve the node voltage column vector and the branch current distribution column vector, and solves the branch local corrosion depth of the grounding system according to the branch current distribution column vector. The application establishes the model of the branch and the node of the grounding system, obtains the branch voltage correlation matrix and the branch voltage drop correlation matrix to solve the node voltage column vector and the branch current distribution column vector, and further solves the branch local corrosion depth of the grounding system, thereby providing a basic algorithm for the influence analysis of the DC grounding electrode on the surrounding grounding system.

Description

Technical Field

[0001] This invention relates to the field of power system grounding technology, specifically to a method and system for assessing local corrosion depth in DC grounding near-field grounding systems. Background Technology

[0002] DC grounding electrodes are an integral part of DC transmission projects. During normal operation, they carry unbalanced currents of tens of amperes. When a fault occurs in a DC transmission project, the DC grounding electrode carries a unipolar return current of thousands of amperes. Existing grounding analysis methods can only assess the overall corrosion of the grounding system and cannot accurately assess the local corrosion impact. To accurately assess the local corrosion impact on the grounding system, the current flowing into the DC grounding electrode and the current field formed by the current flowing into the grounding system must be considered. To address this issue, this invention provides a method for assessing the local corrosion depth of the near-zone grounding system of the DC grounding electrode and a system-wide assessment method, providing a fundamental algorithm for analyzing the impact of the DC grounding electrode on the surrounding grounding system. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for assessing the local corrosion depth of a DC grounding near-field grounding system to solve the problem that existing grounding analysis methods cannot assess the local corrosion of the grounding system.

[0004] The technical solution of this invention: a method and system for assessing local corrosion depth in a DC grounding electrode near-field grounding system, comprising the following steps:

[0005] Step S1: Obtain the total DC current flowing into the ground system based on the simulation calculation results of DC bias or the measurement results of the bias current at the neutral point of the substation grounding transformer.

[0006] Step S2: Establish the grounding system branch and node model; collect the original parameters of the grounding system, which are the position information of each long conductor segment. Based on the position information of the long conductor, coarsely divide each long conductor segment to obtain the intersection of all conductors, and divide the long conductor in half at the intersection to form coarsely divided conductors. For the coarsely divided conductors, set the minimum branch length and finely divide them according to the minimum branch length to obtain the divided conductor branches. The divided conductor branches are short straight conductors with two major geometric attributes: the starting point and the ending point. Based on the starting point coordinates and the ending point coordinates of the conductor branches, form a set of nodes to obtain B branches and N nodes. Based on the relationship between the starting point coordinates, the ending point coordinates, and the node coordinates, obtain the branch voltage correlation matrix and the branch voltage drop correlation matrix.

[0007] Step S3: Solve for the node voltage column vector and branch current dissipation column vector based on the branch voltage correlation matrix and branch voltage drop correlation matrix obtained in step S2;

[0008] Step S4: Solve for the local corrosion depth of the grounding system branches based on the branch current distribution column vector.

[0009] Furthermore, the steps to obtain the branch voltage correlation matrix and the branch voltage drop correlation matrix are as follows:

[0010] Step S21: Organize the starting and ending coordinates of B branches;

[0011] Step S22: Compile N unique node coordinates from all the starting and ending coordinates of the branch roads;

[0012] Step S23: Number the starting point of the i-th branch as j1, the ending point as j2, and set i equal to 1;

[0013] Step S24: The element value in the i-th row and j-1-th column of the branch voltage correlation matrix is ​​0.5, and the element value in the i-th row and j-2-th column is 0.5; the element value in the i-th row and j-1-th column of the branch voltage drop correlation matrix is ​​1, and the element value in the i-th row and j-2-th column is -1.

[0014] Step S25: Determine if i is greater than B; if so, output the branch voltage correlation matrix and the branch voltage drop correlation matrix; otherwise, assign i to i+1 and return to step S23.

[0015] Furthermore, the solution methods for the node voltage column vector and the branch current dissipation column vector are as follows:

[0016] Branch voltage column vector V R The branch current column vector I R and the column vector of DC grounding electrode current to ground I dc The combined effect produces:

[0017] V R =M R I R +M dc I dc (1)

[0018] Among them, M R M is the mutual resistance matrix between branches. dc This is the mutual resistance matrix between the branch and the DC grounding electrode;

[0019] The branch voltage is the average of the voltages at the starting and ending nodes. By the definition of the branch voltage correlation matrix K, we have:

[0020] V R =KV (2)

[0021] Where V is the node voltage column vector;

[0022] Branch voltage drop is generated by the current flowing through the branch, therefore the column vector of branch voltage drop is V.A for:

[0023] V A =ZI A (3)

[0024] Where Z is the current-carrying resistance matrix of the branch, I A This is the column vector of the currents flowing through the branch;

[0025] Branch voltage drop column vector V A The relationship between the node voltage column vector V and the node voltage column vector V is as follows:

[0026] V A =AV (4)

[0027] Where A is the branch voltage drop correlation matrix;

[0028] The total DC current I flowing into the ground system is decomposed into the sum of node conduction current and node dissipation current:

[0029] I = A T I A +K T I R (5)

[0030] Among them, A T Let K be the transpose of the branch voltage drop correlation matrix A. T This is the transpose of the branch voltage correlation matrix K;

[0031] Combining formulas (1) and (6), we get:

[0032]

[0033] Among them, M R -1 M is the mutual resistance matrix between branches. R The inverse matrix, Z -1 It is the inverse matrix of the current-carrying resistance matrix Z of the branch;

[0034] The node voltage column vector V is obtained by solving formula (6);

[0035] Combining equations (1) and (2), we get:

[0036]

[0037] Substituting the node voltage column vector V into formula (7) yields the branch current column vector I. R .

[0038] Furthermore, the calculation method for the local corrosion depth of branches in the grounding system is as follows:

[0039]

[0040] Where Q is the local corrosion depth of the grounding system branch, η is the coefficient of local non-uniform corrosion, and M... e ρ is the equivalent weight of the grounding conductor material, t is the average annual monopolar operating time of the DC transmission project, ρ is the density of the grounding conductor material, L is the length of the branch conductor, and a is the equivalent perimeter of the branch conductor cross-section.

[0041] This invention provides a system for assessing the local corrosion depth of a DC grounding near-field grounding system, comprising a parameter acquisition module, a conductor segmentation module, a matrix generation module, and a corrosion calculation module. The parameter acquisition module acquires the original parameters of the grounding system. The conductor segmentation module performs coarse and fine segmentation of the conductors, dividing long conductors in half at their intersections and further segmenting them according to the minimum branch length. The matrix generation module generates branch voltage correlation matrices and branch voltage drop correlation matrices based on the relationship between the branch start-point coordinates, end-point coordinates, and node coordinates, combined with the rules for writing correlation matrices. The corrosion calculation module calculates the local corrosion depth of the grounding system's branches, based on the branch voltage correlation matrix, the branch voltage drop correlation matrix, and the formula for calculating the local corrosion depth of the grounding system's branches.

[0042] The present invention also provides a non-volatile computer storage medium storing computer-executable instructions that can execute the above-described method and system for assessing local corrosion depth in a DC grounding near-field grounding system.

[0043] The present invention also provides a computer program product, which includes a computer program stored on a non-volatile computer storage medium. The computer program includes program instructions, which, when executed by a computer, cause the computer to execute the above-described method and system for assessing the local corrosion depth of a DC grounding near-field grounding system.

[0044] The present invention also provides an electronic device, comprising: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform a method and system for assessing local corrosion depth in a DC grounding near-field grounding system.

[0045] The beneficial effects of this invention are as follows: This invention establishes a grounding system branch and node model, and obtains the branch voltage correlation matrix and branch voltage drop correlation matrix through the grounding system branch and node model. Then, it solves the node voltage column vector and branch current dissipation column vector, and then solves the local corrosion depth of the grounding system branch. This provides a basic algorithm for analyzing the impact of DC grounding electrodes on the surrounding grounding system. Attached Figure Description

[0046] Figure 1 This is a flowchart of the present invention.

[0047] Figure 2 The flowchart illustrates the establishment of a grounding system branch and node model for this invention.

[0048] Figure 3 This is a schematic diagram of the conductor distribution of the present invention.

[0049] Figure 4 This is a schematic diagram of the node model after partitioning according to the present invention.

[0050] Figure 5 This is a schematic diagram of the branch model after partitioning according to the present invention.

[0051] Figure 6 This is a schematic diagram of the earth resistivity model of the present invention.

[0052] Figure 7 This is a schematic diagram of the branch current distribution results of the present invention.

[0053] Figure 8 This is a schematic diagram showing the results of local corrosion depth in the branch of the present invention. Detailed Implementation

[0054] The invention will now be explained in conjunction with the accompanying drawings.

[0055] refer to Figure 1 A method and system for assessing local corrosion depth in DC grounding near-field grounding systems, with the following steps:

[0056] Step S1: Obtain the total DC current flowing into the ground system based on the simulation calculation results of DC bias or the measurement results of the bias current at the neutral point of the substation grounding transformer.

[0057] refer to Figure 2 Step S2: Establish the grounding system branch and node model; collect the original parameters of the grounding system, which are the position information of each long conductor segment. Based on the position information of the long conductor, coarsely divide each long conductor segment to obtain the intersection of all conductors, and divide the long conductor in half at the intersection to form coarsely divided conductors. For the coarsely divided conductors, set the minimum branch length and finely divide them according to the minimum branch length to obtain the divided conductor branches. The divided conductor branches are short straight conductors with two major geometric attributes: the starting point and the ending point position. The node set is formed by the starting point coordinates and the ending point coordinates of the conductor branches, resulting in B branches and N nodes. Based on the relationship between the starting point coordinates, the ending point coordinates, and the node coordinates, obtain the branch voltage correlation matrix and the branch voltage drop correlation matrix.

[0058] The steps to obtain the branch voltage correlation matrix and the branch voltage drop correlation matrix are as follows:

[0059] Step S21: Organize the starting and ending coordinates of B branches;

[0060] Step S22: Compile N unique node coordinates from all the starting and ending coordinates of the branch roads;

[0061] Step S23: Number the starting point of the i-th branch as j1, the ending point as j2, and set i equal to 1;

[0062] Step S24: The element value in the i-th row and j-1-th column of the branch voltage correlation matrix is ​​0.5, and the element value in the i-th row and j-2-th column is 0.5; the element value in the i-th row and j-1-th column of the branch voltage drop correlation matrix is ​​1, and the element value in the i-th row and j-2-th column is -1.

[0063] Step S25: Determine if i is greater than B; if so, output the branch voltage correlation matrix and the branch voltage drop correlation matrix; otherwise, assign i to i+1 and return to step S23.

[0064] Step S3: Solve for the node voltage column vector and branch current dissipation column vector based on the branch voltage correlation matrix and branch voltage drop correlation matrix obtained in step S2.

[0065] The methods for solving the node voltage column vector and the branch current dissipation column vector are as follows:

[0066] Branch voltage column vector V R The branch current column vector I R and the column vector of DC grounding electrode current to ground I dc The combined effect produces:

[0067] V R =M R I R +M dc I dc (1)

[0068] Among them, M R M is the mutual resistance matrix between branches. dc This is the mutual resistance matrix between the branch and the DC grounding electrode;

[0069] The branch voltage is the average of the voltages at the starting and ending nodes. By the definition of the branch voltage correlation matrix K, we have:

[0070] V R =KV (2)

[0071] Where V is the node voltage column vector;

[0072] Branch voltage drop is generated by the current flowing through the branch, therefore the column vector of branch voltage drop is V. A for:

[0073] V A =ZI A (3)

[0074] Where Z is the current-carrying resistance matrix of the branch, I A This is the column vector of the currents flowing through the branch;

[0075] Branch voltage drop column vector V A The relationship between the node voltage column vector V and the node voltage column vector V is as follows:

[0076] V A =AV (4)

[0077] Where A is the branch voltage drop correlation matrix;

[0078] The total DC current I flowing into the ground system is decomposed into the sum of node conduction current and node dissipation current:

[0079] I = A T I A +K T I R (5)

[0080] Among them, A T Let K be the transpose of the branch voltage drop correlation matrix A. T This is the transpose of the branch voltage correlation matrix K;

[0081] Combining formulas (1) and (6), we get:

[0082]

[0083] Among them, M R -1 M is the mutual resistance matrix between branches. R The inverse matrix, Z -1 It is the inverse matrix of the current-carrying resistance matrix Z of the branch;

[0084] The node voltage column vector V is obtained by solving formula (6);

[0085] Combining equations (1) and (2), we get:

[0086]

[0087] Substituting the node voltage column vector V into formula (7) yields the branch current column vector I. R .

[0088] Step S4: Solve for the local corrosion depth of the grounding system branches based on the branch current distribution column vector.

[0089] The method for calculating the local corrosion depth of a branch in a grounding system is as follows:

[0090]

[0091] Where Q is the local corrosion depth of the grounding system branch, η is the coefficient of local non-uniform corrosion, and M... e ρ is the equivalent weight of the grounding conductor material, t is the average annual monopolar operating time of the DC transmission project, ρ is the density of the grounding conductor material, L is the length of the branch conductor, and a is the equivalent perimeter of the branch conductor cross-section.

[0092] This embodiment provides a system for assessing the local corrosion depth of a DC grounding near-field grounding system, including a parameter acquisition module, a conductor segmentation module, a matrix generation module, and a corrosion calculation module. The parameter acquisition module collects the original parameters of the grounding system. The conductor segmentation module performs coarse and fine segmentation of the conductors, dividing long conductors in half at their intersections and further segmenting them according to the minimum branch length. The matrix generation module generates branch voltage correlation matrices and branch voltage drop correlation matrices, based on the relationship between the branch start-point coordinates, end-point coordinates, and node coordinates, combined with the rules for writing correlation matrices. The corrosion calculation module calculates the local corrosion depth of the grounding system's branches, based on the branch voltage correlation matrix, branch voltage drop correlation matrix, and the formula for calculating the local corrosion depth of the grounding system's branches.

[0093] In another embodiment, a non-volatile computer storage medium is also provided, which stores computer-executable instructions that can execute the above-described method and system for assessing local corrosion depth in a DC grounding near-field grounding system.

[0094] This embodiment also provides a computer program product, which includes a computer program stored on a non-volatile computer storage medium. The computer program includes program instructions, which, when executed by a computer, cause the computer to execute the above-described method and system for assessing the local corrosion depth of a DC grounding near-field grounding system.

[0095] This embodiment also provides an electronic device, including: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to execute a method and system for assessing local corrosion depth in a DC grounding near-field grounding system.

[0096] To verify the evaluation method proposed in this invention, simulation software was used to analyze the local corrosion depth of the near-zone grounding system of a DC grounding electrode in a substation in my country. First, the original parameters of the grounding system were collected, and branch and node models of the grounding system were established. A ground resistivity model was also established to obtain the branch current distribution and local corrosion depth. The minimum branch length was set to 10m, the coefficient η for local non-uniform corrosion was 5, the grounding current was 100A, and the grounding current of the DC grounding electrode was 5kA. (Reference) Figure 6 The earth resistivity model has five layers. The first layer has a resistivity of 60 Ω·m and a thickness of 200 m; the second layer has a resistivity of 150 Ω·m and a thickness of 2800 m; the third layer has a resistivity of 7000 Ω·m and a thickness of 18000 m; the fourth layer has a resistivity of 100000 Ω·m and a thickness of 70000 m; and the fifth layer has a resistivity of 135 Ω·m. (Reference) Figure 3 The straight line represents the conductor of the grounding grid; reference. Figure 4 The number represents the node's ID, and the ID's position indicates the node's location; see reference. Figure 5 The numbers represent the branch numbers; see reference. Figure 7 The numbers represent the magnitude of the branch current. As shown in the figure, the branch current decreases from the edge to the interior of the DC grounding electrode area. (Reference) Figure 7 The numbers represent the local corrosion depth of the branch. As shown in the figure, the local corrosion depth of the branch from the edge to the inside of the DC grounding electrode area shows a trend of decreasing from large to small.

[0097] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for assessing the local corrosion depth of a DC grounding electrode near-field grounding system, characterized in that, The steps are as follows: Step S1: Obtain the total DC current flowing into the ground system based on the simulation calculation results of DC bias or the measurement results of the bias current at the neutral point of the substation grounding transformer. Step S2: Establish the grounding system branch and node model; collect the original parameters of the grounding system, which are the position information of each long conductor segment. Based on the position information of the long conductor, coarsely divide each long conductor segment to obtain the intersection of all conductors, and divide the long conductor in half at the intersection to form coarsely divided conductors. For the coarsely divided conductors, set the minimum branch length and finely divide them according to the minimum branch length to obtain the divided conductor branches. The divided conductor branches are short straight conductors with two major geometric attributes: the start and end positions. Based on the start and end coordinates of the conductor branches, form a set of nodes to obtain B branches and N nodes. Based on the relationship between the start coordinates, end coordinates, and node coordinates of the branches, obtain the branch voltage correlation matrix and the branch voltage drop correlation matrix. Step S21: Organize the starting and ending coordinates of B branches; Step S22: Compile N unique node coordinates from all the starting and ending coordinates of the branch roads; Step S23: Number the starting point of the i-th branch as j1, the ending point as j2, and set i equal to 1; Step S24: The element value in the i-th row and j-1-th column of the branch voltage correlation matrix is ​​0.5, and the element value in the i-th row and j-2-th column is 0.5; the element value in the i-th row and j-1-th column of the branch voltage drop correlation matrix is ​​1, and the element value in the i-th row and j-2-th column is -1. Step S25: Determine if i is greater than B; if yes, output the branch voltage correlation matrix and the branch voltage drop correlation matrix; otherwise, assign i to i+1 and return to step S23. Step S3: Solve for the node voltage column vector and branch current dissipation column vector based on the branch voltage correlation matrix and branch voltage drop correlation matrix obtained in step S2; The node voltage column vector V is obtained by solving formula (6): ； Where I is the total DC current flowing to ground. This is the transpose of the branch voltage correlation matrix K; M is the mutual resistance matrix between branches. R The inverse matrix, M dc I is the mutual resistance matrix between the branch and the DC grounding electrode; dc This is the column vector of the DC grounding electrode currents. This is the transpose of the branch voltage drop correlation matrix A; It is the inverse matrix of the current-carrying resistance matrix Z of the branch; Substituting the node voltage column vector V into formula (7) yields the branch current column vector I. R : ； Step S4: Solve for the local corrosion depth of the grounding system branches based on the branch current distribution column vector.

2. The method for assessing local corrosion depth in a DC grounding electrode near-zone grounding system according to claim 1, characterized in that, The method for calculating the local corrosion depth of a branch in a grounding system is as follows: ； Where Q represents the local corrosion depth of the branch in the grounding system. M is the coefficient for localized non-uniform corrosion. e Let be the equivalent weight of the grounding conductor material, and t be the average annual single-electrode operating time of the DC transmission project. The density of the grounding conductor material, L is the length of the branch conductor, and a is the equivalent perimeter of the branch conductor cross-section.

3. A system for assessing the local corrosion depth of a DC grounding electrode near-zone grounding system, implementing the method for assessing the local corrosion depth of a DC grounding electrode near-zone grounding system according to claim 1 or 2, characterized in that, The system includes a parameter acquisition module, a conductor segmentation module, a matrix generation module, and a corrosion calculation module. The parameter acquisition module acquires the original parameters of the grounding system. The conductor segmentation module performs coarse and fine segmentation of the conductors, dividing long conductors in half at their intersections and further segmenting them according to the minimum branch length. The matrix generation module generates branch voltage correlation matrices and branch voltage drop correlation matrices based on the relationship between the branch start-point coordinates, end-point coordinates, and node coordinates, combined with the rules for writing correlation matrices. The corrosion calculation module calculates the local corrosion depth of the grounding system's branches, using the branch voltage correlation matrix, branch voltage drop correlation matrix, and the formula for calculating the local corrosion depth of the grounding system's branches.

4. A non-volatile computer storage medium, characterized in that, The computer storage medium stores computer-executable instructions that can execute the method for assessing local corrosion depth in a DC grounding electrode near-field grounding system as described in claim 1 or 2.

5. A computer program product, characterized in that, The computer program product includes a computer program stored on a non-volatile computer storage medium, the computer program including program instructions that, when executed by a computer, cause the computer to perform the method for assessing the local corrosion depth of a DC grounding near-field grounding system as described in claim 1 or 2.

6. An electronic device, characterized in that, The system includes at least one processor and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method for assessing local corrosion depth in a DC grounding near-field grounding system as described in claim 1 or 2.

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