Power distribution network section optimization fault positioning method

Abstract

The invention discloses a power distribution network section optimization fault positioning method, and relates to the technical field of single-phase earth fault positioning of a power distribution network. Dividing the multi-branch power distribution network into a main line and branch lines; substituting the arrival time difference of the traveling wave modulus at the tail end of the main line and the line length of the power distribution network into the main section and branch section positioning equations, solving the positioning equations by using a particle swarm algorithm, and calculating to obtain an MSRSE value of each section; the MSRSE values of all the sections are compared, the section with the minimum MSRSE value is a fault section, and the optimal solution of the corresponding equation is the optimal wave velocity and fault distance. According to the method, accurate positioning can be carried out when the fault of the multi-branch power distribution network occurs, the problem that the single-phase earth fault of the power distribution network is difficult to accurately position at present is solved, the influence of inaccurate traveling wave velocity estimation on the positioning accuracy is avoided, and the applicability and the accuracy of a positioning result are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of distribution networks, particularly to the technical field of single-phase grounding fault location in distribution networks, and specifically relates to a method for fault location by optimizing sections of a distribution network. Background Art

[0002] The medium-voltage distribution network in China mainly adopts the non-direct grounding method for the neutral point. When a single-phase grounding fault occurs under this grounding method, the fault characteristics are weak, resulting in difficulty for current protection to effectively cut off the grounding fault. If the fault cannot be quickly isolated, the single-phase grounding fault will develop into two-phase and three-phase faults, ultimately leading to an expanded power outage range and even causing serious safety accidents. The fault location method based on traveling waves has advantages such as being unaffected by the system operation mode and fault type. Studying the distribution network fault location technology based on transient traveling waves has great theoretical value and practical significance for realizing rapid fault isolation, shortening the power supply restoration time, and improving power supply reliability. Compared with the transmission network, the distribution network has numerous branch lines, which increases the difficulty of accurate fault location. Therefore, to improve the power supply reliability, it is urgent to improve the accuracy of fault location.

[0003] Traditional fault traveling wave location methods are divided into single-ended traveling wave location and double-ended traveling wave location. The single-ended traveling wave location calculates the fault distance based on the time delay between the initial traveling wave and the reflected wave from the fault point reaching the detection end; the double-ended traveling wave location uses the time difference between the initial traveling wave wavefronts reaching both ends of the line to perform fault distance measurement. The single-ended method and the double-ended method use the time arrival information of traveling waves at one or both ends of the line to achieve fault location. However, due to the complex topology of the distribution network, it is difficult to achieve accurate fault location only using a small amount of fault traveling wave arrival time information. The wide-area traveling wave method uses the fault traveling wave arrival time information of the entire network to achieve accurate fault location in the distribution network. However, the positioning results of the existing wide-area traveling wave method are affected by the accuracy of the traveling wave velocity. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for fault location by optimizing sections of a distribution network to achieve the purpose of accurate location during faults in a multi-branch distribution network.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for fault location by optimizing sections of a distribution network includes the following steps:

[0007] Step 1: Divide the multi-branch distribution network into a main line and branch lines, and obtain the main line sections N i N j and the branch line sections M i T j .

[0008] Step 2: Based on the arrival time difference of the traveling wave modulus at the end of the main line and the length of the distribution network line, substitute them into the positioning equation to calculate the main line section N i N j and the branch line section M i T j to minimize the sum of the square roots of the sum of the squared errors, that is, the MSRSE value.

[0009] Step 3: Compare the MSRSE values of each section. The section with the minimum MSRSE value is the fault section, and the optimal solution of the corresponding positioning equation is the optimal solution v of the equivalent traveling wave velocity and the line length l from the fault point to node N j or M i of the line.

[0010] Furthermore, the multi-branch distribution network is decomposed into multiple main lines. Each main line includes multiple nodes, and each node is connected to a branch line.

[0011] Furthermore, in Step 2, the arrival time difference of the traveling wave modulus at the end of the main line is the difference between the arrival times of the traveling wave zero mode and the traveling wave line mode components at the end of the main line.

[0012] Furthermore, in Step 2, the particle swarm optimization algorithm is used to solve the positioning equation to calculate the MSRSE values of each section.

[0013] Furthermore, in Step 2, for the main line section N i N j the positioning equation is:

[0014]

[0015] In the formula, n is the number of traveling wave measurement points installed, L NjMx 、L NjMy are respectively the natural line lengths from the downstream node N i N j of the main line section N j to the traveling wave measurement points M x 、M y ,ΔT Mx 、ΔT My are the arrival time differences of the traveling wave modulus measured at the measurement points, L NiNj represents the line length of the section N i N j ,S u is the set of traveling wave positioning devices included in the directly connected upstream part of node N i ,S d is the set of traveling wave positioning devices included in the directly connected downstream part of node N j ,v0 and v α represent the wave velocities of the traveling wave zero mode and the line mode components, and the calculation formulas are respectively and v req represents the ideal equivalent wave velocity, T0 and T α represent the arrival times of the traveling wave zero mode and the line mode components at the traveling wave measurement point, and ΔT represents the difference between the arrival time of the traveling wave zero mode component and the arrival time of the line mode component.

[0016] Furthermore, in step 2, for the branch line section M i T j the positioning equation is:

[0017]

[0018] where n is the number of installed traveling wave measurement points, L MiMx , L MiMy are respectively the natural line lengths from the end node M i T j of the branch section M i to the traveling wave measurement point M x , M y ΔT Mx , ΔT My is the arrival time difference of the traveling wave modulus measured at the measurement point, L MiTj represents the line length of the section M i T j S u is the set of traveling wave positioning devices included in the upstream part directly connected to the node T j v0 and v α represent the wave velocities of the traveling wave zero mode and the line mode components, and their calculation formulas are respectively and v req represents the ideal equivalent wave velocity, T0 and T α represent the arrival times of the traveling wave zero mode and the line mode components at the traveling wave measurement point, and ΔT represents the difference between the arrival time of the traveling wave zero mode component and the arrival time of the line mode component.

[0019] The method of the present invention can accurately locate faults in a multi-branch distribution network, solves the problem of difficult accurate location of single-phase grounding faults in the current distribution network, avoids the influence of inaccurate traveling wave velocity estimation on the location accuracy, and improves the applicability and accuracy of the location results. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly and completely illustrate the technical solutions in the present invention, the drawings used in the present invention will be briefly introduced below. Obviously, the schematic drawings of the present invention are only used to explain the present invention and do not constitute an improper limitation to the present invention. Without creative labor, those of ordinary skill in the art can also obtain other drawings based on these drawings.

[0021] Figure 1 is the flowchart of the method according to an embodiment of the present invention.

[0022] Figure 2 is the structural topology diagram of the multi-branch distribution network according to an embodiment of the present invention.

[0023] Figure 3 is to Figure 2 The multi-branch distribution network in is decomposed into four main lines (a), (b), (c), and (d) as shown in the schematic diagram.

[0024] Figure 4 is Figure 2 The schematic diagram of the main section numbers and branch section numbers of the multi-branch distribution network in. Detailed implementation manners

[0025] The overall concept of the present invention is to divide the multi-branch distribution network into main lines and branch lines, based on the arrival time difference of the traveling wave modulus at the end of the main line and the length of the distribution network line, use the particle swarm optimization algorithm to solve the positioning equations of the main sections and branch sections, and calculate the MSRSE values of each section; compare the MSRSE values of each section, and the section with the smallest MSRSE value is the fault section, and the optimal solution of the corresponding equation is the optimal wave velocity and the fault distance.

[0026] Based on the above concept, the present invention combines a relatively specific embodiment of the distribution network fault, and uses a method for optimizing fault location of distribution network sections described in the present invention to perform optimized fault location on it. The process is as Figure 1 shown, where the distribution network section is a multi-branch distribution network, and its structural topology diagram is as Figure 2 shown.

[0027] Step 1, divide the multi-branch distribution network into main lines and branch lines, and obtain the main line section N i N j and the branch line section M i T j .

[0028] Among them, the multi-branch distribution network is decomposed into multiple main lines, each main line includes multiple nodes, and each node is connected to a branch line.

[0029] In this embodiment, the Figure 2 The multi-branch distribution network shown is decomposed into four main lines, and each main line only contains a single-branch branch, as Figure 3As shown, where (a), (b), (c), and (d) are 4 main lines. The red part in each main line is the main line, and the black part is the branch line. After division, the main line part, branch line part, main section, branch section, etc. of the multi-branch distribution network are obtained, as Figure 4 shown, where the red part is the main line part, the black part is the branch line part, the numbers I to VII are each main section, and the numbers ① to are each branch section.

[0030] Step 2: Based on the arrival time difference of the traveling wave modulus at the end of the main line and the length of the distribution network line, substitute into the positioning equation to calculate the minimum value of the sum of the square roots of the sum of the squares of the errors of the main line section N i N j and the branch line section M i T j , that is, the MSRSE value (the minimization of the sum of the square roots of the sum of the squares of the errors).

[0031] In this embodiment, the positioning equations for the main line section and the branch line section are as described below. Use the particle swarm optimization algorithm to solve the positioning equations and obtain the MSRSE value of each section respectively.

[0032] The positioning equation for the main line section N i N j is:

[0033]

[0034] In the formula, n is the number of traveling wave measurement points installed. In this embodiment, n = 5, L NjMx , L NjMy are respectively the natural line lengths from the downstream node N i N j of the main line section N j to the traveling wave measurement points M x , M y . ΔT Mx , ΔT My are the arrival time differences of the traveling wave modulus measured at the measurement points. L NiNj represents the line length of the section N i N j . S u is the set of traveling wave positioning devices included in the upstream part directly connected to the node N i . S d is the set of traveling wave positioning devices included in the downstream part directly connected to the node N j . v0 and vα Indicates the wave velocities of the traveling wave zero mode and line mode components, and the calculation formulas are respectively and where L0, C0, L1, and C1 are the zero-sequence inductance, capacitance, positive-sequence inductance, and capacitance per unit length of the line respectively, and v req represents the ideal equivalent wave velocity, T0 and T α represent the times when the traveling wave zero mode and line mode components reach the traveling wave measuring point, and ΔT represents the difference between the arrival time of the traveling wave zero mode component and the arrival time of the line mode component.

[0035] Represents the square root of the sum of squared errors, and the objective function min(f NiNj (v, l)) means that the sum of the square roots of the sum of squared errors of section N i N j is minimized.

[0036] For the branch line section M i T j The positioning equation is:

[0037]

[0038] In the formula, n is the number of installed traveling wave measuring points. In this example, n = 5, and L MiMx , L MiMy are respectively the natural line lengths from the end node M i T j of branch section M i to the traveling wave measuring points M x , M y respectively, ΔT Mx , ΔT My are the arrival time differences of the traveling wave mode measured at the measuring points, L MiTj represents the line length of section M i T j , S u is the set of traveling wave positioning devices included in the upstream part directly connected to node T j , and v0 and v α indicate the wave velocities of the traveling wave zero mode and line mode components, and the calculation formulas are respectively and where L0, C0, L1, and C1 are the zero-sequence inductance, capacitance, positive-sequence inductance, and capacitance per unit length of the line respectively, and v req represents the ideal equivalent wave velocity, T0 and T α represent the times when the traveling wave zero mode and line mode components reach the traveling wave measuring point, and ΔT represents the difference between the arrival time of the traveling wave zero mode component and the arrival time of the line mode component.

[0039] Represents the square root of the sum of squared errors, and the objective function min(fMiTj (v, l)) represents section M i T j minimizes the sum of the square roots of the sum of the squared errors of

[0040] In the positioning equations of the above main section and branch sections, the optimal solution l of the positioning equation variable represents the line length from the fault point to node N j or M i with a value range of [0, L NiNj or [0, L MiTj , and the optimal solution v of the equation variable represents the optimal solution of the equivalent traveling wave velocity. Due to the attenuation problem of the traveling wave velocity, v req represents the ideal equivalent wave velocity, so the value range of the equation variable v is [0, v req . By using the particle swarm optimization algorithm to solve the positioning equations of the above main section and branch sections, the MSRSE values of each section can be calculated.

[0041] As Figure 2 shown, two faults are set in the multi-branch distribution network simulation model described in this embodiment: Fault f1 is located in the main section I (section M1T3), 2.3 km away from the T3 branch node; Fault f2 is located in the branch section ③ (section T4M4), 0.5 km away from the M4 end node. For faults f1 and f2, the arrival times of the traveling wave line mode and zero mode components measured by the traveling wave positioning device are shown in Tables 1 and 2 respectively.

[0042] Table 1 Arrival times of traveling wave line mode and zero mode components

[0043]

[0044] Table 2 Arrival times of traveling wave line mode and zero mode components

[0045]

[0046] The time difference between the arrival of the traveling wave modulus at the end of the main line is the difference between the arrival times of the traveling wave zero mode and the traveling wave line mode components at the end of the main line. The time difference of the traveling wave modulus is calculated from the arrival times in Tables 1 and 2 and substituted into the section positioning equation. For faults f1 and f2, the MSRSE values of each section are calculated and shown in Tables 3 and 4 respectively.

[0047] Table 3 MSRSE values of each section

[0048]

[0049] Table 4 MSRSE values of each section

[0050]

[0051] Step 3: Compare the MSRSE values of each section. The section with the minimum MSRSE value is the fault section, and the optimal solution of the corresponding positioning equation is the optimal solution v of the equivalent traveling wave velocity and the line length l from the fault point to node N j or M i of the line.

[0052] In this embodiment, for fault f1, as can be seen from Table 3, the minimum MSRSE value is 0.4456, and the corresponding section is the main trunk section I; for fault f2, as can be seen from Table 4, the minimum MSRSE value is 0.1949, and the corresponding section is the branch section ③. The optimal solutions of each section are shown in Tables 5 and 6 respectively:

[0053] Table 5 Optimal solutions of each section

[0054]

[0055] As can be seen from Table 5, for fault f1, the optimal wave velocity solution of the positioning equation corresponding to the main trunk section I is 3.3637×10 5 km / s, and the optimal distance solution is 2.2914 km.

[0056] Table 6 Optimal solutions of each section

[0057]

[0058] As can be seen from Table 6, for fault f2, the optimal wave velocity solution of the positioning equation corresponding to the branch section ③ is 3.3637×105 km / s, and the optimal distance solution is 0.5051 km.

[0059] The above-described embodiments merely represent one implementation manner of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for optimizing fault location in a distribution network section, characterized in that, It includes the following steps: Step 1: Divide the multi-branch distribution network into a main line and branch lines, and obtain the main line section N i N j and the branch line section M i T j ; Step 2: Based on the arrival time difference of the traveling wave modulus at the end of the main line and the length of the distribution network line, substitute into the positioning equation to calculate the main line section N i N j and the branch line section M i T j The minimum value of the sum of the square roots of the sum of the squared errors, that is, the MSRSE value; Step 3: Compare the MSRSE values of each section. The section with the minimum MSRSE value is the faulty section, and the optimal solution of the corresponding location equation is the optimal solution v of the equivalent traveling wave velocity and the line length l from the fault point to node N j or M i of the line.

2. The optimal fault location method for a distribution network section according to claim 1, characterized in that: In step 1, the multi-branch distribution network is decomposed into multiple main lines, each main line includes multiple nodes, and each node is connected to a branch line.

3. A method for optimizing fault location in a distribution network section according to claim 1, characterized in that: In step 2, the arrival time difference of the traveling wave modulus at the end of the main line is the difference between the arrival times of the zero-mode and line-mode components of the traveling wave at the end of the main line.

4. The optimal fault location method for a distribution network section according to claim 1, characterized in that: In step 2, the particle swarm optimization algorithm is used to solve the positioning equation, and the MSRSE value of each section is calculated.

5. The fault location method for optimizing a distribution network section according to claim 1, characterized in that: In step 2, the main line section N i N j has the following positioning equation: where n is the number of installed traveling wave measurement points, and L NjMx and L NjMy are respectively the natural line lengths from the downstream node N i N j of the main line section N j to the traveling wave measurement points M x and M y , ΔT Mx and ΔT My are the arrival time differences of the traveling wave moduli measured at the measurement points, L NiNj represents the line length of the section N i N j , S u is the set of traveling wave positioning devices included in the directly connected upstream part of the node N i , S d is the set of traveling wave positioning devices included in the directly connected downstream part of the node N j , v0 and v α represent the wave velocities of the traveling wave zero mode and line mode components, and the calculation formulas are respectively and v req represents the ideal equivalent wave velocity, T0 and T α represent the arrival times of the traveling wave zero mode and line mode components at the traveling wave measurement points, and ΔT represents the difference between the arrival time of the traveling wave zero mode component and the arrival time of the line mode component.

6. The optimal fault location method for a distribution network section according to claim 4, characterized in that: In step 2, for the branch line section M i T j the positioning equation is: where n is the number of installed traveling wave measurement points, and L MiMx and L MiMy are respectively the inherent line lengths from the end node M i T j of the branch section M i to the traveling wave measurement point M x and M y ; ΔT Mx and ΔT My are the arrival time differences of the traveling wave moduli measured at the measurement points; L MiTj represents the line length of the section M i T j ; S u is the set of traveling wave positioning devices included in the upstream part directly connected to the node T j ; v0 and v α represent the wave velocities of the traveling wave zero mode and line mode components, and their calculation formulas are respectively and v req represents the ideal equivalent wave velocity; T0 and T α represent the arrival times of the traveling wave zero mode and line mode components at the traveling wave measurement point, and ΔT represents the difference between the arrival time of the traveling wave zero mode component and the arrival time of the line mode component.

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