Alternating current collection line layered fault positioning method based on zero sequence voltage

Abstract

The invention relates to a zero sequence voltage-based alternating current collection circuit layered fault positioning method, which is used for an offshore wind farm and comprises the following steps of: performing branch-free division on a faulted alternating current collection circuit of the offshore wind farm, and dividing the alternating current collection circuit into a plurality of sub-circuits; according to the zero-sequence voltage at the bifurcation of each sub-line and the zero-sequence voltage at the head end and the tail end of each sub-line, zero-sequence parameters at the bifurcation of each sub-line and the head end and the tail end of each sub-line are obtained through calculation, and then a fault line segment of the alternating current collection line is obtained through calculation; and according to the fault line segment, obtaining a specific fault point of the fault line segment of the AC current collection line through an optimization algorithm, and positioning the fault of the AC current collection line. Compared with the prior art, the invention discloses a zero-sequence voltage-based alternating current collection circuit layered fault positioning method suitable for an offshore wind plant, and solves the problem that a traditional power distribution network fault positioning method is not suitable for the offshore wind plant.

Description

Technical Field

[0001] The invention relates to the field of power system fault location, and in particular to a zero-sequence voltage-based layered fault location method for an AC collection line of an offshore wind farm. Background Art

[0002] Offshore wind farms are one of the clean energy solutions that has developed rapidly in recent years as the demand for renewable energy has grown.

[0003] Offshore wind farms have several advantages over onshore wind farms. First, the wind speed at sea is generally higher than on land, which can generate more electricity. Second, the vast sea area is suitable for the layout of large-scale wind farms, and it is far away from densely populated areas, reducing noise and visual pollution. However, the construction and operation of offshore wind farms also face many challenges, including high construction and maintenance costs, complex marine environmental conditions, and potential impacts on the marine ecosystem.

[0004] The fault location method of traditional distribution network usually relies on fixed topology and centralized control system, which is effective in the relatively stable power grid environment in the past. However, there are a large number of renewable energy power generation equipment connected to the distribution network in offshore wind farms. The power grid with a high proportion of renewable energy power generation equipment has higher volatility and instability. The fault location method of traditional distribution network is not suitable for fault location of offshore collector lines. A new fault location method for complex offshore wind farms is needed. Summary of the invention

[0005] The purpose of the present invention is to provide a zero-sequence voltage-based AC collector line layered fault location method, which can realize efficient fault diagnosis and location of wind farms in complex offshore environments, thereby improving the operating efficiency and reliability of the entire wind farm.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for locating layered faults of AC collector lines based on zero-sequence voltage, used in offshore wind farms, comprises:

[0008] Perform branchless division on the AC collector line of the offshore wind farm where the fault occurs, and divide the AC collector line into multiple sub-lines;

[0009] According to the zero-sequence voltage at each sub-line bifurcation and the zero-sequence voltage at the beginning and end of each sub-line, the zero-sequence parameters at each sub-line bifurcation and the beginning and end of each sub-line are calculated, and then the fault line segment of the AC collector line is calculated;

[0010] According to the fault line segment, the specific fault point of the fault line segment of the AC collector line is obtained through the optimization algorithm, and the fault of the AC collector line is located.

[0011] Furthermore, the branchless partitioning process includes:

[0012] Obtain the AC collection line network topology of offshore wind farms;

[0013] Identify all the headends and endends of the AC collection line of the offshore wind farm, where the headend includes the interface node between the AC collection line of the offshore wind farm and the wind turbine, and the endend includes the interface node between the AC collection line of the offshore wind farm and the substation;

[0014] The continuous branchless line connecting the head and the end of the AC collection line of the offshore wind farm is extracted from the network topology of the AC collection line of the offshore wind farm and output as a sub-line.

[0015] Furthermore, the sub-circuit bifurcation is a separation point between sub-circuits with partially overlapping circuits, one side of the separation point is the overlapping part between the sub-circuits, and the other side is the non-overlapping part between the sub-circuits.

[0016] Furthermore, the zero-sequence parameter includes a zero-sequence voltage swell and a zero-sequence current, wherein the zero-sequence voltage swell is the difference between the zero-sequence voltage before the fault and the zero-sequence voltage after the fault.

[0017] Furthermore, the calculation formula of the zero-sequence current is:

[0018]

[0019]

[0020] Among them, f represents the value during the fault period, the subscript (0) represents the value of the zero-sequence physical quantity, n1 and n2 are the detection points, and Z G0 is the zero-sequence impedance of the transformer port where the AC collection lines of the wind farm converge, Z C0 is the fault zero-sequence impedance of the AC collector line, and is the temporary rise of zero-sequence voltage at n1 and n2, and is the zero-sequence current at n1 and n2, is the total zero-sequence current of the sub-circuit.

[0021] Furthermore, the zero-sequence voltage before the fault and the zero-sequence voltage after the fault are obtained by installing measurement units at the branching points of each sub-line and at the beginning and end of each sub-line.

[0022] Furthermore, the process of calculating the fault line segment of the AC collector line includes:

[0023] By installing measurement units at the bifurcation of each sub-circuit and at the beginning and end of each sub-circuit for detection, the zero-sequence voltage at the bifurcation of the sub-circuit and at the beginning and end of the sub-circuit before and after the fault can be obtained in real time;

[0024] The zero-sequence parameters of different detection points are obtained by calculating the zero-sequence voltage;

[0025] According to the zero-sequence parameters and zero-sequence impedance of different detection points in the same sub-line, the voltage rise between the detection points in the sub-line is calculated;

[0026] Compare the voltage rises between the detection points, select the highest voltage rise, and use the line segment between the corresponding two detection points as the fault line segment closest to the fault in this sub-line;

[0027] The weight of the fault line segment closest to the fault in each sub-line in the AC collector line is calculated according to the weight algorithm to obtain the fault line segment.

[0028] Furthermore, the formula of the weight algorithm includes:

[0029] X=[x1 x2…x i …x S-1 x S ],

[0030] Y=[y1 y2…y i …y S-1 y S ],

[0031] J=[j1 j2…j i …j S-1 j S ],

[0032]

[0033] Among them, vector X is the set of faulty line segments closest to the fault. There are S line segments selected as the faulty line segments closest to the fault. i represents the i-th sub-line, x i is the line segment in subline i that is selected as the fault line segment closest to the fault, y i Represents the line segment x in vector X i In how many sub-circuits does j exist? i Represents the line segment x in vector X i The number of times the fault line segment is selected as the closest to the fault, w i For line segment x i The weight of .

[0034] Furthermore, when the specific fault point of the fault line segment of the AC collector line is obtained through the optimization algorithm, the sub-line circuit is converted into a π-type equivalent circuit.

[0035] Furthermore, the formula of the optimization algorithm includes:

[0036]

[0037] Among them, U M0 and U N0 are the zero-sequence voltages at the beginning and end of the current fault line segment, I M0 and I N0 are the zero sequence currents at the head and tail ends, respectively, C Mf is the equivalent capacitance to ground on the front side, C Nf is the equivalent capacitance to ground at the tail end, l is the distance from the fault to the beginning of the fault line segment, L is the total length of the fault line segment, is the zero-sequence voltage at the fault point, and Z0 is the zero-sequence impedance of the current fault line segment.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The present invention discloses a layered fault location method for AC collector lines based on zero-sequence voltage applicable to offshore wind farms, which solves the problem that traditional distribution network fault location methods are not applicable to offshore wind farms. In the invention, the AC collector lines of offshore wind farms with faults are layered, and the complex lines are divided into multiple sub-lines, which reduces the influence of line branches on the fault location accuracy; in multiple sub-lines, fault location calculations are performed based on zero-sequence voltage, which reduces the influence of different wind turbine controls on fault location and improves the accuracy of wind farm fault location; an optimization algorithm is used to calculate fault location, which reduces the influence of the fault resistance on fault location;

[0040] 2. The present invention divides the faulty AC collection line of an offshore wind farm without branches, and installs zero-sequence current measurement elements at key nodes to detect the line during the division. This division and detection method simplifies the system topology and reduces the number of measuring equipment, while also ensuring rapid fault location and isolation, reducing dependence on other non-critical nodes in the line and resource redundancy, reducing the complexity and cost of the line, and ensuring effective monitoring of the electrical status of the entire AC collection line and all sub-lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flow chart of the method of the present invention;

[0042] Figure 2 This is the AC power collection circuit diagram of the wind farm of the present invention;

[0043] Figure 3 The network topology structure of the wind farm system of the present invention;

[0044] Figure 4 This is a sub-circuit diagram of a wind farm according to the present invention;

[0045] Figure 5 This is an example diagram of sub-circuit 3 of the present invention;

[0046] Figure 6 It is the π-type equivalent circuit diagram of the present invention;

[0047] Figure 7 An example diagram is constructed for simulation of an embodiment of the present invention;

[0048] Figure 8 A simplified diagram of the wind farm topology simulated by an embodiment of the present invention;

[0049] Fig. 9 The three-phase zero-sequence current diagram is simulated for an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0051] Example 1

[0052] This embodiment intends to disclose a method for locating layered faults of AC collector lines based on zero-sequence voltage, which is used in offshore wind farms. Figure 1 As shown, the specific steps include:

[0053] Step S1: Figure 2 The AC collection line of the offshore wind farm shown is divided without branches, and the AC collection line is divided into multiple sub-lines.

[0054] The design of AC collection lines for offshore wind farms usually requires consideration of a variety of complex factors, among which the division of branchless sub-lines is a key step. In branchless collection lines, each line is divided into an independent sub-line from the head end to the end of the wind farm, and the head end and the end represent the interface nodes of the wind turbine or substation respectively. This division method simplifies the topological structure of the line and is conducive to the rapid location and isolation of faults.

[0055] The process of branchless partitioning includes:

[0056] Get Figure 3 The AC collector line network topology of an offshore wind farm is shown;

[0057] Identify all the headends and endends of the AC collection line of the offshore wind farm, where the headend includes the interface node between the AC collection line of the offshore wind farm and the wind turbine, and the endend includes the interface node between the AC collection line of the offshore wind farm and the substation;

[0058] Extract the continuous branchless line connecting the head and the end of the AC collection line of the offshore wind farm in the AC collection line network topology structure, such as Figure 4 As shown, it is output as a sub-line.

[0059] There will be some overlap between the extracted sub-routes. The sub-route bifurcation is the separation point between the sub-routes with some overlap. One side of this separation point is the overlapping part between the sub-routes, and the other side is the non-overlapping part between the sub-routes.

[0060] At the separation point and at both ends of the sub-line, measurement units are installed to detect the voltage, such as Figure 4 In each sub-circuit, there are numbers from "1" to "6", which are actually numbers for the nodes where the measuring units are installed. In this embodiment, the AC collector line is divided into three sub-circuits.

[0061] Step S2, according to the zero-sequence voltage at each sub-line branch and the zero-sequence voltage at the beginning and end of each sub-line, the zero-sequence parameters at each sub-line branch and the beginning and end of each sub-line are calculated, and then the fault line segment of the AC collector line is calculated.

[0062] In step S2, the zero-sequence voltage before the fault and the zero-sequence voltage after the fault are obtained by installing measurement units at the branching points of each sub-line and at the beginning and end of each sub-line.

[0063] The zero-sequence parameters include the zero-sequence voltage swell and the zero-sequence current. The zero-sequence voltage swell is the difference between the zero-sequence voltage before the fault and the zero-sequence voltage after the fault. The formula is:

[0064]

[0065] Where V is the voltage, f represents the value during the fault, pf represents the value before the fault, the subscript (0) represents the value of the zero-sequence physical quantity, and n represents the detection point. and are the zero-sequence voltage before and during the fault at the detection point n, respectively.

[0066] The calculation formula of the zero-sequence current is:

[0067]

[0068] Among them, f represents the value during the fault period, the subscript (0) represents the value of the zero-sequence physical quantity, n1 and n2 are the detection points, and Z G0 is the zero-sequence impedance of the transformer port where the AC collection lines of the wind farm converge, Z C0 is the fault zero-sequence impedance of the AC collector line, and is the temporary rise of zero-sequence voltage at n1 and n2, and is the zero-sequence current at n1 and n2, is the total zero-sequence current of the sub-circuit.

[0069] The process of calculating the fault line segment of the AC collector line includes:

[0070] By installing measurement units at the bifurcation of each sub-circuit and at the beginning and end of each sub-circuit for detection, the zero-sequence voltage at the bifurcation of the sub-circuit and at the beginning and end of the sub-circuit before and after the fault can be obtained in real time;

[0071] The zero-sequence parameters of different detection points are obtained by calculating the zero-sequence voltage;

[0072] According to the zero-sequence parameters and zero-sequence impedance of different detection points in the same sub-line, the voltage rise between the detection points in the sub-line is calculated;

[0073] Compare the voltage rises between the detection points, select the highest voltage rise, and use the line segment between the corresponding two detection points as the fault line segment closest to the fault in this sub-line;

[0074] The weight of the fault line segment closest to the fault in each sub-line in the AC collector line is calculated according to the weight algorithm, and the line segment with the highest weight is the fault line segment.

[0075] In this embodiment, the process of calculating the zero-sequence current and the fault line segment closest to the fault is selected as follows: Figure 5 Sub-line 3 is shown as an example.

[0076] For detection points 1 and 5 in sub-circuit 3, the calculation formula for zero-sequence current is:

[0077]

[0078] Where f represents the value during the fault period, the subscript (0) represents the value of the zero-sequence physical quantity, and Z G0 is the zero-sequence impedance of the transformer port where the AC collection lines of the wind farm converge, Z C0 is the fault zero-sequence impedance of the AC collector line, and is the zero-sequence voltage temporary rise at detection point 1 and detection point 5, and is the zero sequence current at detection point 1 and detection point 5, is the total zero-sequence current of sub-circuit 3.

[0079] After the zero-sequence current at the detection point is calculated, the calculation formula for the zero-sequence voltage of the line segment between each detection point in sub-line 3 is:

[0080]

[0081] Among them, m and n are the number of detection points. is the voltage rise calculated at the end point m by the current injected at the detection point n, is the total zero-sequence voltage temporary rise of sub-line 3, and Error is the line segment zero-sequence voltage temporary rise.

[0082] The formula for the weighted algorithm includes:

[0083] X=[x1 x2…x i …x S-1 x S ],

[0084] Y=[y1 y2…y i …y S-1 y S ],

[0085] J=[j1 j2…j i …j S-1 j S ],

[0086]

[0087] Among them, vector X is the set of faulty line segments closest to the fault. There are S line segments selected as the faulty line segments closest to the fault. i represents the i-th sub-line, x i is the line segment in subline i that is selected as the fault line segment closest to the fault, y i Represents the line segment x in vector X i In how many sub-circuits does j exist? i Represents the line segment x in vector X i The number of times the fault line segment is selected as the closest to the fault, w i For line segment x i The weight of .

[0088] Step S3, according to the fault line segment, the specific fault point of the fault line segment of the AC collector line is obtained through an optimization algorithm, and the fault of the AC collector line is located.

[0089] After the fault line segment is obtained, due to the short interval between wind turbines in offshore wind farms, in order to improve the distance measurement accuracy, the cable adopts a π-type equivalent circuit, and uses the principle that the zero-sequence voltage of the fault line segment is equal everywhere to deduce the zero-sequence voltage of the middle point from the zero-sequence data at both ends, such as Figure 6 Shown

[0090] The formula for the optimization algorithm includes:

[0091]

[0092] Among them, UM0 and U N0 are the zero-sequence voltages at the M and N ends of the current fault line segment, I M0 and I N0 are the zero sequence currents at the M and N terminals, C Mf is the equivalent capacitance to ground on the M side, C Nf is the equivalent capacitance to ground on the N side, l is the distance from the fault to the M end of the fault line segment, L is the total length of the fault line segment, is the zero-sequence voltage at the fault point, and Z0 is the zero-sequence impedance of the current fault line segment.

[0093] Solving the equation will yield the unknown l, which is the location of the fault point.

[0094] If the above method is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0095] Example 2

[0096] This embodiment is based on the above-mentioned embodiment 1, and is intended to disclose the actual simulation of locating faults using the AC collector line layered fault locating method based on zero-sequence voltage.

[0097] To verify the performance of the layered positioning method for offshore wind power collection lines, Figure 7 As shown in the figure, a wind farm simulation model is built in the real-time digital simulation system (RTDS) platform. The fault location algorithm is compiled in the server containing Visual Studio through the program. The RTDS data inputs the fault data into the server containing the fault location algorithm through the GTNET communication board to complete the fault location function. The main transformer of the offshore wind farm is grounded through a small resistor, and the grounding resistance of the main transformer is 60Ω. The wind turbines all use direct-drive wind turbine models, with a total of 16 units, and the rated capacity is 2.5MW.

[0098] The line data of the wind farm simulation model built in this simulation is shown in Table 1 below.

[0099] Table 1 Line parameters of offshore wind farms

[0100]

[0101] like Figure 8 As shown in the figure, according to the AC collector line hierarchical fault location method based on zero-sequence voltage, the AC collector line topology of the wind farm is simplified and divided into three sub-lines, among which 1, 2, 3, 4, 5, 6, 7, 14, 15 and 16 wind turbines are sub-line 1 paths, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 are sub-line 2 paths, and 1, 2, 3, 4, 5, 6, 7, 11, 12 and 13 are sub-line 3 paths.

[0102] Scenario 1: Asymmetric ground faults at different locations.

[0103] In order to examine the influence of different positions of asymmetric ground fault on the positioning performance, faults are set in the lines of multiple sub-lines and tested, and 50Ω excess impedance is set at different positions.

[0104]

[0105] Where, d r d e They represent the actual fault location distance and the calculated fault distance respectively; L is the actual length of the fault line.

[0106] The simulation results of scenario 1 are shown in Table 2 below.

[0107] Table 2 Simulation results of positioning performance under different fault types

[0108]

[0109] In the table, Δd max % is the maximum value of Δd% under different fault positions. The experimental results can reflect the different fault types of the AC collector line. The experimental results can realize the accurate positioning of the fault. The detected fault three-phase zero-sequence current is as follows: Fig. 9 shown.

[0110] Scenario 2: In order to verify the positioning effect of the wind turbine fault ride-through control method, we Figure 8 In the simulation, a fault is set in the collector line 2-3. A phase A ground fault and AB phase AB ground fault are set in the 2-3 line segment respectively. The fault point is 800 meters away from one end of 2, and the transition resistance is 0 ohm.

[0111] The simulation results of scenario 2 are shown in Table 3 below.

[0112] Table 3 Simulation results of positioning performance under fan fault ride-through

[0113]

[0114] It can be seen from Table 3 that there is no obvious correlation between the ranging accuracy and the wind turbine fault ride-through strategy, and for the fault ride-through control strategy under the national standard, the ranging error is very small. It can be concluded that the positioning scheme can effectively suppress the disturbance of the wind turbine to the line and accurately locate the fault of the line.

[0115] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for locating layered faults of AC collector lines based on zero-sequence voltage, used in offshore wind farms, characterized in that: The method comprises: Perform branchless division on the AC collector line of the offshore wind farm where the fault occurs, and divide the AC collector line into multiple sub-lines; According to the zero-sequence voltage at each sub-line bifurcation and the zero-sequence voltage at the beginning and end of each sub-line, the zero-sequence parameters at each sub-line bifurcation and the beginning and end of each sub-line are calculated, and then the fault line segment of the AC collector line is calculated; According to the fault line segment, the specific fault point of the fault line segment of the AC collector line is obtained through the optimization algorithm, and the fault of the AC collector line is located.

2. The method for locating layered faults of AC collector lines based on zero-sequence voltage according to claim 1, characterized in that: The branchless partitioning process comprises: Obtain the AC collection line network topology of offshore wind farms; Identify all the headends and endends of the AC collection line of the offshore wind farm, where the headend includes the interface node between the AC collection line of the offshore wind farm and the wind turbine, and the endend includes the interface node between the AC collection line of the offshore wind farm and the substation; The continuous branchless line connecting the head and the end of the AC collection line of the offshore wind farm is extracted from the network topology of the AC collection line of the offshore wind farm and output as a sub-line.

3. The method for locating AC collector line layered faults based on zero-sequence voltage according to claim 1, characterized in that: The sub-circuit bifurcation is a separation point between sub-circuits with partially overlapping circuits, one side of the separation point is the overlapping part between the sub-circuits, and the other side is the non-overlapping part between the sub-circuits.

4. The method for locating AC collector line layered faults based on zero-sequence voltage according to claim 1, characterized in that: The zero-sequence parameters include a zero-sequence voltage swell and a zero-sequence current, wherein the zero-sequence voltage swell is the difference between the zero-sequence voltage before the fault and the zero-sequence voltage after the fault.

5. The method for locating layered faults of AC collector lines based on zero-sequence voltage according to claim 4, characterized in that: The calculation formula of the zero-sequence current is: Among them, f represents the value during the fault period, the subscript (0) represents the value of the zero-sequence physical quantity, n1 and n2 are the detection points, and Z G0 is the zero-sequence impedance of the transformer port where the AC collection lines of the wind farm converge, Z C0 is the fault zero-sequence impedance of the AC collector line, and is the temporary rise of zero-sequence voltage at n1 and n2, and is the zero-sequence current at n1 and n2, is the total zero-sequence current of the sub-circuit.

6. The method for locating layered faults of AC collector lines based on zero-sequence voltage according to claim 4, characterized in that: The zero-sequence voltage before the fault and the zero-sequence voltage after the fault are obtained by installing measurement units at the branching points of each sub-line and at the beginning and end of each sub-line.

7. The method for locating AC collector line layered faults based on zero-sequence voltage according to claim 1, characterized in that: The process of calculating the fault line segment of the AC collector line includes: By installing measurement units at the bifurcation of each sub-circuit and at the beginning and end of each sub-circuit for detection, the zero-sequence voltage at the bifurcation of the sub-circuit and at the beginning and end of the sub-circuit before and after the fault can be obtained in real time; The zero-sequence parameters of different detection points are obtained by calculating the zero-sequence voltage; According to the zero-sequence parameters and zero-sequence impedance of different detection points in the same sub-line, the voltage rise between the detection points in the sub-line is calculated; Compare the voltage rises between the detection points, select the highest voltage rise, and use the line segment between the corresponding two detection points as the fault line segment closest to the fault in this sub-line; The weight of the fault line segment closest to the fault in each sub-line in the AC collector line is calculated according to the weight algorithm to obtain the fault line segment.

8. The method for locating layered faults of AC collector lines based on zero-sequence voltage according to claim 7, characterized in that: The formula of the weight algorithm includes: X=[x1 x2…x i …x S-1 x S ], Y=[y1 y2…y i …y S-1 yes S ], J=[j1 j2…j i …j S-1 j S ], Among them, vector X is the set of faulty line segments closest to the fault. There are S line segments selected as the faulty line segments closest to the fault. i represents the i-th sub-line, x i is the line segment in sub-line i that is selected as the fault line segment closest to the fault, y i Represents the line segment x in vector X i In how many sub-circuits does j exist? i Represents the line segment x in vector X i The number of times the fault line segment is selected as the closest to the fault, w i For line segment x i The weight of .

9. The method for locating layered faults of AC collector lines based on zero-sequence voltage according to claim 1, characterized in that: When the specific fault point of the fault line segment of the AC collector line is obtained through the optimization algorithm, the sub-line circuit is converted into a π-type equivalent circuit.

10. The method for locating layered faults of AC collector lines based on zero-sequence voltage according to claim 1, characterized in that: The formula of the optimization algorithm includes: Among them, U M0 and U N0 are the zero-sequence voltages at the beginning and end of the current fault line segment, I M0 and I N0 are the zero sequence currents at the head and tail ends, respectively, C Mf is the equivalent capacitance to ground on the front side, C Nf is the equivalent capacitance to ground at the tail end, l is the distance from the fault to the beginning of the fault line segment, L is the total length of the fault line segment, is the zero-sequence voltage at the fault point, and Z0 is the zero-sequence impedance of the current fault line segment.

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