Method for optimally arranging measuring points of grounding grid of substation

Abstract

The invention discloses an optimal arrangement method for measuring points of a substation grounding grid, and belongs to the technical field of power systems. Before the substation grounding grid is diagnosed, the number and the positions of the optimal measurement points are output. And key areas and sensitive positions are concentrated, so that the test workload is saved, and the diagnosis accuracy is improved. Different measuring point optimization arrangement schemes are provided for different substations, and the early warning capability of corrosion faults of a grounding grid is enhanced. And operation and maintenance personnel can quickly locate problems, so that the troubleshooting time is shortened, the maintenance efficiency is improved, and the maintenance cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of power systems, and in particular to a method for optimizing the arrangement of measuring points of a substation grounding grid. Background Art

[0002] As an important part of the power system, the substation grounding grid is mainly used to provide safe electrical grounding for substation equipment to ensure personal safety and normal operation of equipment. The grounding grid introduces current into the ground to quickly eliminate fault current in the power system, thereby avoiding damage to personnel and equipment. Corrosion of the grounding grid is one of the main causes of defects in the grounding grid, causing many accidents. Therefore, detection and diagnosis of grounding grid corrosion is of vital importance to correctly understand the operating status of the grounding grid, timely discover potential problems and take corresponding measures.

[0003] At present, there are three main methods for diagnosing grounding grid corrosion: electromagnetic field method, electrochemical measurement method and electrical network theory method. Among them, the electrical network theory method is simple in principle, easy to implement, not affected by electromagnetic interference, and does not require soil excavation. It is a more commonly used method. The electrical network method injects DC current between the nodes of the grounding grid, measures the voltage between the two injected nodes, and obtains the corresponding grounding grid port resistance through voltage and current calculation. Then, the electrical network theory and Tellegen's theorem are used to solve the branch resistance of the grounding grid according to the port resistance. The actual branch resistance obtained by the solution is compared with the theoretical resistance of the branch to determine the corrosion degree of the branch. However, in practice, the number of existing equipment grounding down conductors in substations is small, and the measurement points that can be obtained by injecting DC current as observation points are limited, and the branches that can be solved are limited to the range where the down conductors are located. However, since the grounding grid is buried underground, if a lead-out terminal is added to each node of the grounding grid for measurement, the implementation is cumbersome and the construction workload is large, and the cost is too high. Therefore, the present invention proposes a method for optimizing the arrangement of grounding grid measurement nodes. The method is used to determine the observation nodes of the grounding grid and to achieve accurate diagnosis of grounding grid branch corrosion with as few measurement nodes as possible. Summary of the invention

[0004] In order to solve the defects of the above-mentioned prior art, the present invention proposes a method for optimizing the arrangement of measuring points of a substation grounding grid. The method for optimizing the arrangement of measuring points of a substation grounding grid of the present invention outputs the optimal number and position of measuring points before detecting the substation grounding grid, thereby saving the workload of detection and improving the accuracy of detection.

[0005] The technical solution of the present invention is achieved in this way: A method for optimizing the arrangement of measuring points of a substation grounding grid, the specific steps are as follows: Step 1: According to the ground grid structure, establish the ground grid correlation matrix and ground grid parameter vector: (1) According to the substation grounding grid design drawings, analyze the topological structure between its branches and nodes, and generate the grounding grid association matrix A. (2) According to the grounding network branch in the substation grounding network design drawing, the nominal value of the grounding network branch resistance is calculated, and the nominal value vector of the grounding network branch resistance is calculated to obtain the branch conductance matrix Y b , b represents the number of branches, (3) Calculate the grounding grid node admittance matrix Y n =AY b A T ; Step 2: Select all nodes of the grounding grid as measurement points to obtain a measurement point set; Step 3: Generate a measurement matrix based on the measurement point set and calculate the column correlation coefficient of the measurement matrix ,in, is the measurement matrix, r is the number of measurement nodes in the selected measurement point set; Step 4: Analyze the observability of the measurement matrix and determine whether the correlation coefficient of the measurement matrix columns satisfies: , Z represents the number of corroded branches of the grounding grid. If it is satisfied, the current set of measurement points is output and the process goes to step 6. If it is not satisfied, the process goes to step 5. Step 5: Remove one measurement point from the measurement point set and find the column with the smallest increase in correlation coefficient The measurement point set, return to step 3; Step 6: Determine the best set of measurement nodes and deploy them on site according to the location, that is, output the set of best node numbers { }.

[0006] In the present invention, in step 1, , ,in, It represents the value of the i-th row and j-th column in the grounding grid association matrix, i represents the node number, j represents the branch number, and n represents the number of nodes.

[0007] In the present invention, in step 1, the nominal resistance value of the grounding network branch j is , j = 1,2,3,...,b, is the resistivity of the grounding grid branch, is the length of grounding grid branch j, is the cross-sectional area of ​​the grounding grid branch j, and the nominal value vector of the grounding grid branch resistance , branch conductance matrix , is a diagonal matrix with diagonal elements The other elements are 0.

[0008] In the present invention, in step 2, the measurement point set is {1, 2, L, ..., n}.

[0009] In the present invention, in step 3, step 3 includes: (1) According to the measurement point set, a reference node is randomly selected to generate the current vector ; (2) Calculate the grounding grid node voltage matrix ,in, is the inverse matrix of the node admittance matrix, is the injection current matrix; (3) Calculate the sensitivity between each node and each branch to obtain the measurement matrix of the grounding grid ; (4) Calculate the measurement matrix The column correlation coefficient .

[0010] In the present invention, in step 3, , , where r is the number of measurement nodes in the selected measurement point set, n is the number of nodes, represents the element in the i-th row and j-th column of the current vector, The injected DC current is specified.

[0011] In the present invention, in step 3, the sensitivity ,in, .

[0012] In the present invention, in step 3, the measurement matrix .

[0013] In the present invention, in step 3, the column correlation coefficient , express The kth column of represents the inner product of the kth column and the jth column, Represents the magnitude of a vector.

[0014] In the present invention, in step 5, step 5 includes: (1) Remove one measurement point from the measurement point set in order to obtain a new measurement point set; (2) Calculate the column correlation coefficients of the new measurement matrix in sequence according to the method in step 3; (3) Find the column with the smallest increase in correlation coefficient That is the measurement point set, return to step 3.

[0015] The method for optimizing the arrangement of measuring points of the substation grounding grid of the present invention has the following beneficial effects: before diagnosing the substation grounding grid, the optimal number and position of measuring points are output. The key areas and sensitive positions are concentrated, which not only saves the workload of testing, but also improves the accuracy of diagnosis. Different measurement point optimization arrangement schemes are proposed for different substations to enhance the early warning capability of grounding grid corrosion faults. Operation and maintenance personnel can quickly locate problems, reduce the time of troubleshooting, improve maintenance efficiency, and reduce maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of a method for optimizing the arrangement of measuring points of a substation grounding grid according to the present invention; Figure 2 Schematic diagram of the grounding grid of the present invention. DETAILED DESCRIPTION

[0017] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. Embodiment 1

[0018] like Figure 1 As shown, the present embodiment discloses a method for optimizing the arrangement of measuring points of a substation grounding grid, and the specific steps are as follows: Step 1: According to the ground grid structure, establish the ground grid association matrix and ground grid parameter vector.

[0019] (1) According to the substation grounding grid design drawings, analyze the topological structure between its branches and nodes and generate the grounding grid association matrix , ,in, It represents the value of the i-th row and j-th column in the grounding grid association matrix, i represents the node number, j represents the branch number, n represents the number of nodes, and b represents the number of branches.

[0020] (2) Based on the material, length and other parameters of the grounding network branch in the substation grounding network design drawings, calculate the nominal value of the grounding network branch resistance , j = 1,2,3,...,b, is the resistivity of the grounding grid branch, is the length of grounding grid branch j, is the cross-sectional area of ​​the grounding grid branch j, and the nominal value vector of the grounding grid branch resistance , branch conductance matrix , is a diagonal matrix with diagonal elements The other elements are 0.

[0021] (3) Calculate the grounding grid node admittance matrix Y n=AY b A T .

[0022] Step 2: Select all nodes of the grounding grid as measurement points and obtain the measurement point set {1, 2, L, …, n}.

[0023] Step 3: Generate a measurement matrix and calculate the column correlation coefficient of the measurement matrix.

[0024] (1) According to the measurement point set, a reference node is randomly selected and the current vector is generated according to the following rules: : , , where r is the number of measurement nodes in the selected measurement point set, n is the number of nodes, represents the element in the i-th row and j-th column of the current vector, The injected DC current is specified.

[0025] (2) Calculate the grounding grid node voltage matrix ,in, is the inverse matrix of the node admittance matrix, is the injection current matrix.

[0026] (3) Calculate the sensitivity between each node and each branch ,in, , the measurement matrix of the grounding grid : .

[0027] (4) Calculate the measurement matrix The column correlation coefficient , column correlation coefficient , express The kth column of represents the inner product of the kth column and the jth column, Represents the magnitude of a vector.

[0028] Step 4: Analyze the observability of the measurement matrix.

[0029] (1) Determine whether the correlation coefficient of the measurement matrix columns satisfies the following formula: , Z represents the number of corroded branches in the grounding grid.

[0030] (2) If satisfied, output the current set of measurement points and go to step 6; if not satisfied, go to step 5.

[0031] Step 5: Remove a certain measurement point from the measurement point set and find the minimum increase in the column correlation coefficient The set of measurement points.

[0032] (1) Remove the measurement points from the measurement point set one by one in order to obtain a new measurement point set.

[0033] (2) Calculate the column correlation coefficients of the new measurement matrix in sequence according to the method in step 3.

[0034] (3) Find the column with the smallest increase in correlation coefficient. The measurement point set is returned to step 3.

[0035] Step 6: Determine the best set of measurement nodes and deploy them on-site according to location.

[0036] (1) Output the set of best node numbers { }.

[0037] (2) Provide on-site donations according to location. Embodiment 2

[0038] like Figure 2 As shown, this embodiment applies the technical solution of the present invention to a specific substation. The nodes and branches of the substation grounding network are numbered as follows: Figure 1 As shown, the circle represents the grounding grid node, and the rectangle represents the grounding grid branch. In the embodiment, it is assumed that branch 1 and branch 10 are corroded, and their branch resistance is set to 15 ohms, and the other branches are in good condition, and the branch resistance is 1 ohm.

[0039] (1) According to the substation grounding grid design drawings, analyze the topological structure between its branches and nodes, and generate the grounding grid association matrix A. Taking the 3*3 node grounding grid network data as an example, calculate the grounding grid association matrix A. ,The size of the grounding grid association matrix is ​​9×12, that is, the grounding grid has 9 nodes and 12 branches.

[0040] (2) According to the material and length of the grounding grid branch, the nominal value vector of the branch resistance of the grounding grid is obtained: .

[0041] (3) Based on the obtained branch resistance nominal value vector, the branch conductance matrix is ​​calculated as , .

[0042] (4) Select all nodes of the grounding grid as measurement points and obtain the measurement point set { }.

[0043] (5) Inject current into all nodes except the reference node =20A, set node 9 as the reference node, and the rest of the nodes as measurement points to generate the current vector , , and then by Y n =AYb A T Get the node conductance matrix , and then according to the formula Get the voltage of each node , , and then substitute into the formula The measurement matrix can be obtained from , .

[0044] (6) According to the formula Calculate the measurement matrix The column correlation coefficient , .

[0045] (7) Set the initial value Z = 2.

[0046] (8) Judgment Is it true? Substitute it into Not true. Then proceed to the next step.

[0047] (9) Then remove a certain measurement point in the grounding grid and recalculate the column correlation coefficient of the new measurement matrix according to the method in step (6) to find the measurement point set with the smallest increase in column correlation coefficient.

[0048] (10) Recalculate the measurement matrix and column correlation coefficient of the new measurement point set. Determine whether , if satisfied, then output the current set of measurement points; if not satisfied, then return to (8).

[0049] (11) Repeat step (10) for several iterations, and finally get the removed node set The column correlation coefficient ,at this time Established.

[0050] (12) Output the node number set of the best measurement point: .

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for optimizing the arrangement of measuring points of a substation grounding grid, characterized in that: The specific steps are as follows: Step 1: According to the ground grid structure, establish the ground grid correlation matrix and ground grid parameter vector: (1) According to the substation grounding grid design drawings, analyze the topological structure between its branches and nodes, and generate the grounding grid association matrix A. (2) According to the grounding network branch in the substation grounding network design drawing, the nominal value of the grounding network branch resistance is calculated, and the nominal value vector of the grounding network branch resistance is calculated to obtain the branch conductance matrix Y b , b represents the number of branches, (3) Calculate the grounding grid node admittance matrix Y n =AY b A T ; Step 2: Select all nodes of the grounding grid as measurement points to obtain a measurement point set; Step 3: Generate a measurement matrix based on the measurement point set and calculate the column correlation coefficient of the measurement matrix ,in, is the measurement matrix, r is the number of measurement nodes in the selected measurement point set; Step 4: Analyze the observability of the measurement matrix and determine whether the correlation coefficient of the measurement matrix columns satisfies: , Z represents the number of corroded branches of the grounding grid. If it is satisfied, the current set of measurement points is output and the process goes to step 6. If it is not satisfied, the process goes to step 5. Step 5: Remove one measurement point from the measurement point set and find the minimum increase in the column correlation coefficient The measurement point set, return to step 3; Step 6: Determine the best set of measurement nodes and deploy them on site according to the location, that is, output the set of best node numbers { }.

2. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 1 is characterized in that: In step 1, , ,in, It represents the value of the i-th row and j-th column in the grounding grid association matrix, i represents the node number, j represents the branch number, and n represents the number of nodes.

3. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 1 is characterized in that: In step 1, the nominal resistance value of the grounding grid branch j is , j = 1,2,3,...,b, is the resistivity of the grounding grid branch, is the length of grounding grid branch j, is the cross-sectional area of ​​the grounding grid branch j, and the nominal value vector of the grounding grid branch resistance , branch conductance matrix , is a diagonal matrix with diagonal elements The other elements are 0.

4. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 1 is characterized in that: In step 2, the measurement point set is {1,2,L,…,n}.

5. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 1 is characterized in that: In step 3, step 3 includes: (1) According to the measurement point set, a reference node is randomly selected to generate the current vector ; (2) Calculate the grounding grid node voltage matrix ,in, is the inverse matrix of the node admittance matrix, is the injection current matrix; (3) Calculate the sensitivity between each node and each branch to obtain the measurement matrix of the grounding grid ; (4) Calculate the measurement matrix The column correlation coefficient .

6. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 5 is characterized in that: In step 3, , , where r is the number of measurement nodes in the selected measurement point set, n is the number of nodes, represents the element in the i-th row and j-th column of the current vector, The injected DC current is specified.

7. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 5 is characterized in that: In step 3, the sensitivity ,in, .

8. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 5 is characterized in that: In step 3, the measurement matrix .

9. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 5, characterized in that: In step 3, the column correlation coefficients , express The kth column of represents the inner product of the kth column and the jth column, Represents the magnitude of a vector.

10. The method for optimizing the arrangement of measuring points of the substation grounding grid according to claim 1, characterized in that: In step 5, step 5 includes: (1) Remove one measurement point from the measurement point set in order to obtain a new measurement point set; (2) Calculate the column correlation coefficients of the new measurement matrix in sequence according to the method in step 3; (3) Find the column with the smallest increase in correlation coefficient That is the measurement point set, return to step 3.

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