Topology identification method for low-voltage transformer area

Abstract

The invention discloses a topology identification method for a low-voltage transformer area, and the method comprises the steps: obtaining the current feature and voltage feature data of a meter box through an intelligent terminal disposed at a node of each to-be-observed and to-be-analyzed meter box in the transformer area; calculating mutual impedance between meter box nodes, and constructing a mutual impedance matrix depicting electrical topology in a table area; and performing layer-by-layer clustering on the nodes of the meter box to be observed based on a hierarchical clustering method to obtain a topological structure of the whole transformer area. According to the low-voltage transformer area topology identification method, the mutual impedance is directly related to the position information of the nodes, the topology is calculated by utilizing the mutual impedance information, and the accuracy is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply and distribution, and in particular to a method for identifying low-voltage substation topology. Background Art

[0002] The topological relationship of low-voltage substations refers to the tree-like subordinate relationship between transformers, outlet cabinets, branch boxes, and meter boxes in the substations. Accurate substation topological relationships help to quickly locate faults, improve power supply reliability, conduct line loss analysis, and manage overload in substations, so that power management departments can formulate more scientific operation and maintenance plans and management strategies. In reality, some substations will archive and save the topological relationship at the beginning of construction, but due to subsequent expansion of the substation, re-planning, or the addition of new users, it is possible that the topology changes and the archive information are not updated in time, resulting in the actual topological relationship being inconsistent with the archive information; some old communities or rural power substations lack archival information of topological relationships due to historical reasons such as limited conditions and poor management. When the archival information of the topology is no longer reliable, it becomes very important to accurately identify the topological relationship. Summary of the invention

[0003] Technical purpose: In view of the defects in the prior art, the present invention discloses a method for identifying low-voltage substation topology. The mutual impedance is directly related to the location information of the node, and the topology is calculated using the mutual impedance information, which is more accurate.

[0004] Technical solution: In order to achieve the above technical objectives, the present invention adopts the following technical solution.

[0005] A method for identifying low voltage area topology comprises the following steps:

[0006] S1. Each meter box to be observed and analyzed in the low-voltage area is regarded as a meter box node in the topology, and the current characteristic and voltage characteristic data of the meter box are obtained by using the intelligent terminal installed at the meter box node;

[0007] S2, calculate the mutual impedance between the meter box nodes and construct the mutual impedance matrix that describes the electrical topology in the substation area;

[0008] S3. Cluster the observation meter box nodes layer by layer based on the hierarchical clustering method in combination with the mutual impedance matrix to obtain the topological structure of the entire substation area.

[0009] Beneficial effects:

[0010] 1. The present invention does not require additional equipment to be installed, and the topology of the platform area can be calculated using the existing user electricity consumption data, which is easy to promote;

[0011] 2. Mutual impedance is directly related to the location information of the node. Using mutual impedance information to calculate the topology is more accurate.

[0012] 3. This method is applicable to various topological structures such as radial and fishbone, and is universal. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a topological structure of an embodiment of the present invention;

[0014] Figure 2 The figure is a flow chart of a method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0016] As attached Figure 1 and attached Figure 2 As shown, a low voltage area topology identification method of this embodiment includes the following steps:

[0017] S1. Each meter box to be observed and analyzed in the low-voltage area is taken as a meter box node in the topology. The current characteristic and voltage characteristic data of the meter box are obtained by using the intelligent terminal installed at the meter box node; the current characteristic is the transient change of current greater than x amperes generated by the meter box within z seconds, and the voltage characteristic is the transient change of voltage greater than y volts generated by the meter box within z seconds; wherein z∈[0.01, 0.02], x∈[8, 15], y∈[0.1, 0.2];

[0018] S2, calculate the mutual impedance between the meter box nodes, and construct the mutual impedance matrix R that describes the electrical topology in the substation area; S2 includes the following steps:

[0019] S2.1. Use I a ={i a1 ,i a2 , ..., i an}, where n is the number of power consumption events, i an is the current characteristic collected when the nth power consumption event occurs; according to the current characteristic sequence I of the meter box node A a For each current characteristic in the meter box, find the voltage characteristic value of the meter box node B caused by it. The voltage characteristic sequence of the meter box node B is expressed by U b = {u b1 ,u b2 , ..., u bn} indicates that it is important to know that after each power consumption event occurs, the corresponding voltage and current will change, that is, each power consumption event has a set of corresponding voltage characteristics and current characteristics;

[0020] S2.2, according to the voltage characteristic sequence U of the meter box node B b and the current characteristic sequence I of the meter box node A a For each set of corresponding values ​​in , an impedance r is calculated. The calculation formula of impedance r is:

[0021]

[0022] Among them, r abx is the impedance value calculated using the current and voltage characteristics of the xth power consumption event, u bx is the voltage characteristic of the xth power consumption event, i ax is the current characteristic of the xth power consumption event;

[0023] All impedance values ​​are expressed in the impedance series R ab = {r ab1 , r ab2 , ..., r abx , ..., r abn}express;

[0024] S2.3. Calculate the impedance sequence R ab The mean value r ab_avg and standard deviation σ ab , put R ab Not in (r ab_avg -3σ ab , r ab_avg +3σ ab ) range, and then find R ab The median of the remaining impedance values ​​r ab_mid , as the mutual impedance between meter box node A and meter box node B, denoted as r ab ;

[0025] S2.4. Calculate the mutual impedance between any two meter box nodes according to the method of S2.1-S2.3 to obtain the mutual impedance matrix The elements r on the diagonal of the mutual impedance matrix are 11 ,……,r mm are all 0, and m is the total number of meter box nodes.

[0026] Taking the topological structure of the substation shown in Figure 1 as an example, the mutual impedance matrix can be obtained according to the current characteristic sequence and voltage characteristic sequence of each terminal node:

[0027]

[0028] S3, cluster the observation meter box nodes layer by layer based on the hierarchical clustering method in combination with the mutual impedance matrix to obtain the topological structure of the entire substation area. S3 includes the following steps:

[0029] S3.1. In the mutual impedance matrix R, select the largest impedance value r pq , 1≤p≤m, 1≤q≤m, merge its corresponding nodes p and q. According to the node types of nodes p and q, there are three cases:

[0030] S3.1.1. When nodes p and q are both table box nodes, the merge process is to create a new virtual node v n , virtual node v n The member set Mv n For {p, q}, virtual node v n Self-impedance For r pq ;

[0031] S3.1.2. When nodes p and q contain a virtual node and a table box node, compare r pq The difference between the self-impedance of the virtual node Is it greater than the impedance threshold of the newly added virtual node? If it is greater than the threshold, the merge processing is performed when both nodes p and q are meter box nodes; if it is less than the threshold, no new virtual node is generated, and the meter box node is merged into another virtual node, that is, the meter box node is added to the member set of the virtual node, and r pq The average value of the self-impedance of the virtual node is taken as the updated self-impedance of the virtual node;

[0032] S3.1.3. When nodes p and q are both virtual nodes, compare r pq The difference between the mean self-impedance of the two virtual nodes Is it greater than the impedance threshold of the newly added virtual node? are the self-impedances of the two virtual nodes respectively. If they are greater than the threshold, the merge processing is the same as when nodes p and q are both meter box nodes; if they are less than the threshold, no new virtual node is generated, and the members of node p are added to the member set of node q, and the Update the self-impedance of node q and delete node p. Set the impedance threshold of the newly added virtual node to 0.002 ohms.

[0033] S3.2. Calculate the newly created or updated virtual node v n The mutual impedance with other nodes z. Take v n The average value of the mutual impedance of any meter box node included and any meter box node included in z is taken as v n and the mutual impedance of z.

[0034] S3.3, update the mutual impedance matrix R. Specifically includes two operations:

[0035] S3.3.1. For v n For each member node in the member set of , remove the corresponding row and column in the mutual impedance matrix R.

[0036] S3.3.2. Using v calculated in S3.2 n and the mutual impedance value of other nodes, and v n The corresponding rows and columns are added to the mutual impedance matrix R.

[0037] S3.4, repeat S3.1-3.2 until they are finally merged into a virtual node.

[0038] Specifically, taking the mutual impedance matrix in this embodiment as an example, each impedance value in the matrix is ​​a cluster. First, find the maximum value 0.052, which is the mutual impedance of node 4 and node 5. 4 and 5 are both meter box nodes, and are directly merged into a virtual node v1. The member set of v1 is {4, 5}, and the self-impedance of v1 is r v1 is 0.052. Update the mutual impedance matrix R, delete the rows and columns corresponding to nodes 4 and 5, and add the rows and columns corresponding to node v1. The last row and column of the matrix are the mutual impedances of node v1 and other nodes.

[0039]

[0040] In this matrix, the maximum impedance value is found again, which is 0.41, which is the mutual impedance between node 6 and node v1. Compare this value with the self-impedance of node v1, which is 0.052. The absolute value of the difference exceeds 0.002, so nodes 6 and v1 need to generate a new virtual node v2. The member set of v2 is {6, v1}, and the self-impedance of v2 is 0.042. Update the mutual impedance matrix R, delete the rows and columns where nodes 6 and node v1 are located, and add the rows and columns where node v2 is located. The last row and column of the matrix are the mutual impedance between node v2 and other nodes.

[0041]

[0042] In this matrix, we find the maximum impedance value again, which is 0.038. It is the mutual impedance of node 1 and node 2. These two nodes are both meter box nodes, and they are directly merged into a virtual node v3. The member set of v3 is {1, 2}, and the self-impedance of v3 is 0.038. Update the mutual impedance matrix R, delete the rows and columns where nodes 1 and 2 are located, and add the rows and columns where node v3 is located. The last row and column of the matrix are the mutual impedance between v3 and other nodes.

[0043]

[0044] In this matrix, the maximum impedance value is found again, which is 0.038, which is the mutual impedance between node v3 and node 3. The absolute value of the difference between this value and the self-impedance of node v3, 0.038, is less than 0.002. Therefore, no new virtual node is generated, and node 3 is merged into node v3, that is, the member set of v3 is updated to {1, 2, 3}, and the self-impedance of v3 is 0.038. Update the mutual impedance matrix R, delete the row and column of node 3, and get:

[0045]

[0046] In this matrix, the maximum impedance value is found again, which is 0.011, which is the mutual impedance of nodes v2 and v3. The absolute value of the difference between this value and the average self-impedance of nodes v2 and v3 is greater than 0.002, so nodes v1 and v2 are merged into one node. Since all nodes are merged, the final virtual node after the merger is the transformer node. At this point, the topology result calculation is completed, and the topology structure is as shown in the attached figure. Figure 1 shown.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for identifying low voltage area topology, characterized in that: The following steps are involved: S1. Each meter box to be observed and analyzed in the low-voltage area is regarded as a meter box node in the topology, and the current characteristic and voltage characteristic data of the meter box are obtained by using the intelligent terminal installed at the meter box node; S2, calculate the mutual impedance between the meter box nodes and construct the mutual impedance matrix that describes the electrical topology in the substation area; S3. Cluster the observation meter box nodes layer by layer based on the hierarchical clustering method in combination with the mutual impedance matrix to obtain the topological structure of the entire substation area.

2. A low voltage area topology identification method according to claim 1, characterized in that: S2 includes the following steps: S2.

1. Use I a ={i a1 ,i a2 , ..., i an }, where n is the number of power consumption events, i an is the current characteristic collected when the nth power consumption event occurs; according to the current characteristic sequence I of the meter box node A a For each current characteristic in the meter box, find the voltage characteristic value of the meter box node B caused by it. The voltage characteristic sequence of the meter box node B is expressed by U b = {u b1 ,u b2 , ..., u bn }express; S2.2, according to the voltage characteristic sequence U of the meter box node B b and the current characteristic sequence I of the meter box node A a For each set of corresponding values ​​in , an impedance r is calculated. The calculation formula of impedance r is: Among them, r abx is the impedance value calculated using the current and voltage characteristics of the xth power consumption event, u bx is the voltage characteristic of the xth power consumption event, i ax is the current characteristic of the xth power consumption event; All impedance values ​​are expressed in the impedance series R ab = {r ab1 , r ab2 , ..., r abx , ..., r abn }express; S2.

3. Calculate the impedance sequence R ab The mean value r ab_avg and standard deviation σ ab , put R ab Not in (r ab_avg -3σ ab , r ab_avg +3σ ab ) range, and then find R ab The median of the remaining impedance values ​​r ab_mid , as the mutual impedance between meter box node A and meter box node B, denoted as r ab ; S2.

4. Calculate the mutual impedance between any two meter box nodes according to the methods of S2.1-S2.3 to obtain the mutual impedance matrix R. The elements r on the diagonal of the mutual impedance matrix are 11 ,……,r mm are all 0, and m is the total number of meter box nodes.

3. A low voltage area topology identification method according to claim 1, characterized in that: S3 includes the following steps: S3.

1. In the mutual impedance matrix R, select the largest impedance value r pq , 1≤p≤m, 1≤q≤m, merge its corresponding nodes p and q; S3.

2. Calculate the newly created or updated virtual node v n Mutual impedance with other nodes z; S3.3, update the mutual impedance matrix R; S3.4, repeat S3.1-3.2 until they are finally merged into a virtual node.

4. A low voltage area topology identification method according to claim 3, characterized in that: According to the node types of nodes p and q, there are three cases: S3.1.

1. When nodes p and q are both table box nodes, the merge process is to create a new virtual node v n , virtual node v n The member set Mv n For {p, q}, virtual node v n Self-impedance For r pq ; S3.1.

2. When nodes p and q contain a virtual node and a table box node, compare r pq The difference between the self-impedance of the virtual node Is it greater than the impedance threshold of the newly added virtual node? If it is greater than the threshold, the merge processing is performed when both nodes p and q are meter box nodes; if it is less than the threshold, no new virtual node is generated, and the meter box node is merged into another virtual node, that is, the meter box node is added to the member set of the virtual node, and r pq The average value of the self-impedance of the virtual node is taken as the updated self-impedance of the virtual node; S3.1.

3. When nodes p and q are both virtual nodes, compare r pq The difference between the mean self-impedance of the two virtual nodes Is it greater than the impedance threshold of the newly added virtual node? are the self-impedances of the two virtual nodes respectively. If they are greater than the threshold, the merge processing is the same as when nodes p and q are both meter box nodes; if they are less than the threshold, no new virtual node is generated, and the members of node p are added to the member set of node q, and the Update the self-impedance of node q and delete node p.

5. A low voltage area topology identification method according to claim 4, characterized in that: The impedance threshold of the newly added virtual node is set to 0.002 ohms.

6. A low voltage area topology identification method according to claim 3, characterized in that: S3.2 includes: taking v n The average value of the mutual impedance of any meter box node included and any meter box node included in z is taken as v n and the mutual impedance of z.

7. A low voltage area topology identification method according to claim 3, characterized in that: S3.3 includes: S3.3.

1. For v n For each member node in the member set of , remove the corresponding row and column in the mutual impedance matrix R. S3.3.

2. Using v calculated in S3.2 n and the mutual impedance value of other nodes, and v n The corresponding rows and columns are added to the mutual impedance matrix R.

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