A node voltage-based fault section location technology for power distribution networks

Abstract

The application discloses a kind of distribution network fault interval positioning technology based on node voltage, mainly includes the following steps: first, according to the topological structure of distribution network and line parameter generation node admittance matrix, and establish node current solving equation.Judge whether short-circuit fault occurs according to each node voltage.When short-circuit fault occurs, according to the variation of each node positive sequence voltage before and after fault of distribution network, the variation of each node positive sequence current is solved and is effectively handled.When only one node current variation is not 0, then the node is fault point;When only two node currents are not 0, then it is judged that the fault is located on the line between the two nodes, and the fault point position is calculated;When multiple node current variations are not 0, take the node with the maximum node current modulus value as the node that is not 0, make the positive sequence current variation of other nodes 0, then it is judged that the fault is located on the line between the two nodes and the fault point position is calculated.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection, and particularly relates to the fault location technology of distribution network based on node voltage. Background Technology

[0002] Rapid and accurate fault location in distribution networks is a prerequisite for timely isolation of faulty areas and restoration of power to non-faulty areas, and is of great significance for improving system reliability. Statistics show that over 80% of power grid faults occur on the distribution network side. With the integration of numerous distributed power sources into the distribution network, creating an active network with bidirectional flow of normal operating power and fault current, fault location has become more complex, rendering traditional location algorithms inapplicable. Furthermore, traditional fault location methods require strict data synchronization and high sampling frequencies; devices meeting these conditions are expensive, hindering the practical application of many fault location methods. Therefore, researching new technologies for accurate distribution network fault location is an urgent technical challenge. Summary of the Invention

[0003] To address the technical problems mentioned in the background, this invention provides a distribution network fault location technology based on node voltage. This technology can accurately locate the fault range based on the magnitude of the current magnitude at each node when a short-circuit fault occurs in the distribution network.

[0004] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows:

[0005] A fault location technology for distribution networks based on node voltage includes the following steps:

[0006] Step 1: Generate the node admittance matrix Y of the distribution network based on the topology and line parameters of the distribution network. N×N ;

[0007] Step 2: Establish the node current solution equation based on node voltage measurement;

[0008] Step 3: Determine whether a short-circuit fault has occurred in the distribution network based on the node voltage;

[0009] Step 4: When a fault occurs, measure and calculate the positive sequence voltage changes of each node in the distribution network before and after the fault.

[0010] Step 5: Construct the positive sequence network diagram of the distribution network, and solve for the positive sequence current change at each node based on the positive sequence voltage change value at each node.

[0011] Step 6: Validation of the positive sequence current change at each node yields the magnitude ΔI of the positive sequence current change at each node. i(1) ′;

[0012] Step 7: After the effective processing of the node positive sequence current change, when ΔI i(1) If only one node in the fault zone has a non-zero current, then the location of that non-zero node is the fault location point, and the fault zone judgment ends.

[0013] Step 8: After the effective processing of the node positive sequence current change, when ΔI i(1) If only two nodes in the line have non-zero current, the fault is determined to be located on the line between these two nodes, and the location of the fault point in the line section is calculated.

[0014] Step 9: After the effective processing of the node positive sequence current change, ΔI i(1) When multiple node current changes are not zero, select the two nodes with the largest current magnitudes as the non-zero nodes, and set the positive sequence current changes of the other nodes to zero. Then continue to step 8 to calculate the fault location.

[0015] The beneficial effects of adopting the above technical solution are as follows:

[0016] This invention is a novel method for locating fault zones in a distribution network by utilizing the magnitude of the change in node current after a fault at each node. This invention effectively solves the problem of locating short-circuit fault zones in distribution networks. Furthermore, this invention features simple calculations, requires only steady-state voltage values, and avoids strict data synchronization and high sampling frequencies. This invention has wide applicability and is not affected by false fault points. This invention can accurately locate fault zones in distribution networks, effectively reducing fault investigation time and improving the level of distribution automation. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention;

[0018] Figure 2 This is a schematic diagram of the IEEE 33-node topology;

[0019] Figure 3 This is a schematic diagram showing the changes in current at each node when phase-A ground faults occur at nodes 3 and 27 respectively.

[0020] Figure 4 This is a graph showing the changes in current at each node in section 3-4 at different distances for different fault types;

[0021] Figure 5 This is a graph showing the changes in current at each node for different fault types and distances in sections 27-28. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings.

[0023] This invention proposes a method for locating fault sections in distribution networks based on node voltage, such as... Figure 1 As shown, it includes the following steps:

[0024] A method for locating fault sections in a distribution network based on node voltage includes the following steps:

[0025] Step 1: Generate the node admittance matrix Y of the distribution network based on the topology and line parameters of the distribution network. N×N As shown in equation (1).

[0026]

[0027] In the formula: N is the number of nodes in the distribution network topology, Y i·i The self-admittance of node i, Y i·j This is called the mutual admittance between nodes i and j, y i·0 Let y be the admittance of node i to ground. i·j Let be the branch admittance between node i and node j.

[0028] Step 2: Establish the node current solution equation based on node voltage measurement as shown in equation (2).

[0029]

[0030] In the formula: Let be the node current at node i. Measure the voltage at node j;

[0031] Step 3: Determine whether a short circuit fault has occurred in the distribution network based on the node voltage. If equation (3) is satisfied, then it is determined that a short circuit fault has occurred in the distribution network.

[0032] U i ≤U z·d·i (3)

[0033] In the formula: U i Let U be the measured voltage magnitude of node i, where U is the voltage magnitude of node i. z·d·i U can be chosen based on the actual situation. z·d·i = (0.2~0.8)U N·i U N·i Let be the rated voltage of node i.

[0034] Step 4: When a fault occurs, measure and calculate the positive sequence voltage changes of each node in the distribution network before and after the fault.

[0035] The calculation method for the positive sequence voltage change of the i-th node is shown in equation (4):

[0036]

[0037] In the formula: The positive sequence voltage of node i in the system was obtained from the measured voltage data before the fault. This refers to the positive sequence voltage of node i in the system, obtained from the measured voltage data after the fault. It is the change in positive-sequence voltage before and after a fault at node i;

[0038] Step 5: Construct the positive sequence network diagram of the distribution network, and solve for the positive sequence current change of each node based on the positive sequence voltage change value of each node.

[0039]

[0040] In the formula: Let be the change in the positive sequence current at the i-th node. Let be the positive-sequence voltage change at node j;

[0041] Step 6: Effective processing of positive sequence current changes at each node.

[0042]

[0043] Where: ε i ε is the allowable error value. i =0.05I i·l·max I i·l·max ΔI is the maximum load current of the upstream line of node i during normal operation. i(1) Let ΔI be the magnitude of the positive sequence current change at node i. i(1) ′ represents the magnitude of the positive sequence current change of node i after the effective processing.

[0044] Step 7: After the effective processing of the node positive sequence current change, when ΔI i(1) If only one node in the fault zone has a non-zero current, then the location of that non-zero node is the fault location point, and the fault zone judgment ends.

[0045] Step 8: After the effective processing of the node positive sequence current change, when ΔI i(1) If only two nodes in the line have non-zero current, the fault is determined to be located on the line between these two nodes, and the location of the fault point in the line section can be calculated according to formula (7).

[0046]

[0047] Where: ΔI p(1) ′ and ΔI q(1) ′ is ΔI i(1) The non-zero elements in ' are α, which is the proportion of the fault point's location within the line section to the line length.

[0048] Step 9: After the effective processing of the node positive sequence current change, ΔI i(1) When multiple nodes in the fault have non-zero current changes, the two nodes with the largest current magnitudes are selected as the non-zero nodes, and the positive sequence current changes of the other nodes are set to zero, as shown in formula (8). Then, step 8 is executed to calculate the fault location.

[0049]

[0050] Where: ΔI l(1) ′ and ΔI m(1) The effective processing of the positive sequence current change at nodes l and m, ΔI i(1) ′ max1 and ΔI i(1) ′ max2 For ΔI i(1) The two largest values ​​in ′.

[0051] The present invention will be described below through examples:

[0052] A simulation diagram of the IEEE 33-node circuit was built using MATLAB / SIMULINK, with the circuit topology as follows: Figure 2 As shown. The simulation sampling frequency is 4kHz, the reference voltage at the beginning of the power network in the simulation is 12.66kV, the neutral point is directly grounded, and the total network load is 5084.26 + j2547.32 kVA. There are a total of 33 nodes, 32 branches, and 5 tie switch branches in the system. For the area between nodes 0 and 1, the line impedance is very small and can be regarded as the equivalent impedance of the power supply. When generating the node admittance matrix, the reference node 0 needs to be removed. Therefore, the power saving admittance matrix is ​​of order 32, and the area that can be located is the 32 areas contained in nodes 1 to 33 in the distribution network.

[0053] (1) As Figure 3 The diagram shows the current changes at each node when two fault points (nodes 3 and 27) are set up in an example of this invention, and the fault type is single-phase grounding. Figure 3 It can be seen that when the fault occurs at node 3, after effectively processing the current changes at each node, ΔI i(1) Only ΔI is present in ′ 3(1) =2278.18, and the magnitude of the current change at all other nodes is 0, therefore the fault location result is node 3; when the fault occurs at node 27, there is a significant non-zero value in the current change vector of each node, corresponding to node 27. After validating the current change of each node, ΔI i(1) Only ΔI is present in ′ 27(1)=533.18, and the magnitude of the current change at all other nodes is 0, indicating that node 27 is the location. The above optimized results demonstrate that the fault location method is effective.

[0054] (2) Figure 4 As shown, in an example of this invention, five fault points were set in sections 3-4 respectively. The localization effect of different fault locations and fault types was discussed at 10%, 20%, 50%, 70%, and 90% of the line at nodes 3 and 4. Figure 5 It can be seen that when the fault occurs in section 3-4, at 70% of the line, and the fault type is a phase-to-phase short circuit, the node current change has two non-zero values ​​ΔI after vectorization. 3(1) ′=800.01,ΔI 4(1) =1866.35, calculate α = 0.7000, the location result is segment 3-4, α = 0.7000. When the fault occurs in segment 3-4, at 70% of the line, and the fault type is a single-phase ground fault, there are two significant non-zero values ​​ΔI in the node current change vector. 3(1) =533.36 and ΔI 4(1) =1244.30, calculate α = 0.7000, the location result is segment 3-4, α = 0.7000. The location accuracy of different fault types is shown in Table 1, and the results show that the fault location method is effective.

[0055] Table 1. Location results of different fault types at different distances on the lines of nodes 3 and 4.

[0056]

[0057] As can be seen from Table 1, under different fault types in distribution network section 3-4, the fault section location is still very accurate when the fault occurs in different places in the section.

[0058] (3) Figure 5 As shown in the example of this invention, five fault points were set in sections 27-28 respectively. The localization effect of different fault locations and fault types was discussed at 10%, 20%, 50%, 70%, and 90% of the line at nodes 27 and 28. Figure 5 It can be seen that when the fault occurs in section 27-28, at 90% of the line, and the fault type is a three-phase short circuit, the node current change has two non-zero values ​​ΔI after vectorization. 27(1) ′=131.51, ΔI 28(1) =1184.25, calculate α = 0.9001, the location result is section 27-28, α = 0.9001, the relative error is 0.0001. When the fault occurs in section 27-28, at 90% of the line, and the fault type is a two-phase-to-ground short circuit, there are two significant non-zero values ​​ΔI in the node current change vector.27(1) =87.65 and ΔI 28(1) =789.56, calculate α = 0.9001, the location result is segment 27-28, α = 0.9001, and the relative error is 0.0001. The location accuracy for different fault types is shown in Table 2, and the results show that the fault location method is effective.

[0059] Table 2. Location results for different distances and fault types on the lines at nodes 27 and 28.

[0060]

[0061] As can be seen from Table 2, under different fault types in distribution network sections 27-28, the fault section location remains very accurate even when the fault occurs in different locations within the section.

[0062] (4) In the example, four fault points were set at 20% of sections 3-4, 18-19, 22-23, and 27-28, respectively. The fault type was a two-phase short circuit (AB phase). 1% noise was added to the voltage measurement data. When the fault occurred in section 3-4, the node current change had two non-zero values ​​ΔI after vectorization. 3(1) ′=2505.00,ΔI 4(1) =625.89, calculate α = 0.1999, the location result is segment 3-4, α = 0.1999, the relative error is 0.0001. When the fault occurs in segment 18-19, the node current change vector has two non-zero values ​​ΔI after effective processing. 18(1) = 3945.87, ΔI 19(1) =986.16, calculate α = 0.1999, the location result is segment 18-19, α = 0.1999, the relative error is 0.0001. When the fault occurs in segment 22-23, the node current change vector has two non-zero values ​​ΔI after effective processing. 22(1) =2013.82, ΔI 23(1) =503.33, calculate α = 0.2000, the location result is segment 22-23, α = 0.2000. When the fault occurs in segment 27-28, the node current change vector has two non-zero values ​​ΔI after effective processing. 27(1) =604.38, ΔI 28(1) =151.24, calculate α = 0.2002, the location result is segment 27-28, α = 0.2002, and the relative error is 0.0002. Currently, the measurement error of most voltage measuring devices remains between 0.1% and 0.5%, therefore, the noise immunity of this algorithm can meet the requirements of practical applications. The results after the above optimization process demonstrate the effectiveness of the fault location method.

Claims

1. A fault location technology for distribution networks based on node voltage, characterized in that: Includes the following steps: Step 1: Generate the node admittance matrix of the distribution network based on the topology and line parameters of the distribution network. The node admittance matrix The formula is: ； In the formula: N is the number of nodes in the distribution network topology, Y i·i Let Y be the self-admittance of node i. i·j Let y be the mutual admittance between nodes i and j. i·0 Let y be the admittance of node i to ground. i·j Let be the branch admittance between node i and node j; Step 2: Establish the node current solution equation based on node voltage measurement; Step 3: Determine whether a short-circuit fault has occurred in the distribution network based on the node voltage; Step 4: When a short-circuit fault occurs, measure and calculate the positive sequence voltage changes at each node of the distribution network before and after the fault. Step 5: Construct the positive sequence network diagram of the distribution network, and solve for the positive sequence current change at each node based on the positive sequence voltage change value at each node. ; Step 6: Optimize the positive sequence current change of each node to obtain the magnitude of the positive sequence current change of each node. ; Step 7: After the effective processing of the node positive sequence current change, when If only one node has a non-zero current, then the location of that non-zero node is the fault location point, and the fault interval judgment ends. Step 8: After the effective processing of the node positive sequence current change, when If only two nodes have non-zero current, the fault is determined to be located on the line between these two nodes, and the location of the fault point in that line section is calculated. Step 9: After the effective processing of the node positive sequence current change, When multiple nodes have non-zero current changes, select the two nodes with the largest current magnitudes as the non-zero nodes, and set the positive sequence current changes of the other nodes to 0; then continue to step 8 to calculate the fault location. In step 2, the node current solution equation based on node voltage measurement is established as shown in equation (2): (2) In the formula: For nodes node current, For nodes Node voltage measurement; The effective processing of the positive sequence current change of each node in step 6 is as shown in equation (6): (6) In the formula: For the allowable error value, , for The maximum load current of the upstream line during normal operation at the node. For nodes The magnitude of the positive sequence current change. For nodes Node after positive sequence current change quantification The magnitude of the positive sequence current change; In step 8, the location of the fault point in the line section is calculated according to formula (7): (7) In the formula: and for Non-zero elements in the middle, This represents the proportion of the fault location within the line section to the total length of the line.

2. The fault location technology for distribution networks based on node voltage according to claim 1, characterized in that: In step 5, the positive sequence network diagram of the distribution network is constructed, and the positive sequence current change of each node is calculated based on the positive sequence voltage change value of each node, as shown in equation (5): (5) In the formula: For the first The change in positive sequence current at each node. For nodes The positive sequence voltage change.

3. The distribution network fault section location technology based on node voltage according to claim 1, characterized in that: After the effective processing of the node positive sequence current change in step 7, when If only one node has a non-zero current, then the location of that non-zero node is the fault location point, and the fault interval judgment ends.

4. The fault location technology for distribution networks based on node voltage according to claim 1, characterized in that: After the effective processing of the node positive sequence current change in step 9, When multiple nodes have non-zero current changes, take the two nodes with the largest current magnitudes as the non-zero nodes, and set the positive sequence current changes of the other nodes to 0, as shown in formula (8); then continue to execute step 8 to calculate the fault location. （8） In the formula: and After the node positive sequence current change was effectively processed, the node and The magnitude of the positive sequence current change. and for The two largest values ​​in the middle.

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