CN110927526B - Power distribution network fault line selection method based on zero-sequence current waveform fractal box dimension - Google Patents

Power distribution network fault line selection method based on zero-sequence current waveform fractal box dimension Download PDF

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CN110927526B
CN110927526B CN201911269884.XA CN201911269884A CN110927526B CN 110927526 B CN110927526 B CN 110927526B CN 201911269884 A CN201911269884 A CN 201911269884A CN 110927526 B CN110927526 B CN 110927526B
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fault
sequence current
line
feeder line
feeder
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CN110927526A (en
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姚康
黄继盛
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Lincang Power Supply Bureau of Yunnan Power Grid Co Ltd
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Lincang Power Supply Bureau of Yunnan Power Grid Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/088—Aspects of digital computing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

Abstract

The invention relates to a power distribution network fault line selection method based on zero sequence current waveform fractal box dimension, and belongs to the technical field of power system relay protection. Firstly, acquiring transient zero sequence current of each feeder line; after that, for each feederCarrying out fractal box dimension calculation on the transient zero-sequence current; to be provided with
Figure DEST_PATH_IMAGE002
As the ordinate, with
Figure DEST_PATH_IMAGE004
Plotting each feeder line as an abscissa, on a coordinate axis
Figure DEST_PATH_IMAGE002A
~
Figure 402249DEST_PATH_IMAGE004
A straight line after fitting; and selecting the fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis. The fault line selection method utilizes the fractal box dimension difference of the transient zero-sequence current curves of all the feeder lines when the fault occurs to perform fault line selection, can obviously distinguish the fault feeder line from the sound feeder line, is simple and convenient to operate, is beneficial to the identification of the far-end high-resistance fault, and is easy to popularize and apply.

Description

Power distribution network fault line selection method based on zero-sequence current waveform fractal box dimension
Technical Field
The invention belongs to the technical field of power system relay protection, and particularly relates to a power distribution network fault line selection method based on performance difference of zero-sequence current waveform fractal box dimension on a two-dimensional plane.
Background
The problem of single-phase earth fault line selection of a power distribution network is an important subject to be solved by a power distribution system built and reconstructed in China. Due to the reasons of small fault current, unobvious fault characteristics and the like after the single-phase earth fault occurs, the existing line selection method has poor effect in actual operation. Although the existing power distribution network single-phase earth fault line selection method based on information fusion makes up the defects of a single line selection scheme and improves the line selection accuracy, most line selection methods ignore the correlation among fault information, only rely on a large number of samples for training, and cannot be guaranteed to be applicable to all fault conditions. Although the low-current grounding system has the advantages of ensuring the reliability and continuity of power supply and the like, the low-current grounding system has the defects that when a certain phase has a grounding fault, the fault current is very small, the fault characteristic is not obvious, and the fault feeder line is very difficult to find. If the fault feeder cannot be found out and the fault can be eliminated for a long time, the safe operation of the power system is bound to be greatly threatened. Especially in the complex system that the neutral point earthed through the arc suppression coil, can promptly and accurately find out trouble feeder and eliminate the trouble, to realizing distribution system automation having important meaning.
Although there are many methods and devices for selecting lines of a power distribution network, the method and device have poor effect in practical application and still have many problems. In many power supply departments, a method of switching off the feeders one by one is still adopted to troubleshoot faulty feeders, and if the faulty feeders are still not found after the feeders are switched off in sequence, a plurality of feeders may have faults at the same time, so that the fault range is enlarged, and the safe and stable operation of the system is influenced. At present, the problem of line selection of a power distribution network is recognized as a difficult problem which is not completely solved. The research on the line selection method of the single-phase earth fault of the power distribution network and the research on the line selection device have great significance and urgent market demands. The environment of the distribution network is complex and changeable, and the fault conditions are also various. The fault line selection is carried out only by means of one fault characteristic, so that the situations of multi-selection, wrong selection or selection omission and the like easily occur, and the timely search and fault elimination of a fault feeder line are not facilitated. Therefore, how to overcome the defects of the prior art is a problem which needs to be solved urgently in the technical field of relay protection of the power system at present.
Disclosure of Invention
The invention aims to solve the defects of the prior art and provides a power distribution network fault line selection method based on zero-sequence current waveform fractal box dimension.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a power distribution network fault line selection method based on zero-sequence current waveform fractal box dimension comprises the following steps:
collecting transient zero sequence current of each feeder line;
performing fractal box dimension calculation on the transient zero-sequence current of each feeder line;
the specific method for calculating the fractal box dimension comprises the following steps: taking a small box with the side length of epsilon, covering the transient zero-sequence current to be measured by using the small box, wherein N (epsilon) represents the number of non-empty boxes during covering, and calculating the box dimension through epsilon and N (epsilon); then adjusting the side length of the small box, and carrying out box dimension calculation for multiple times;
drawing a straight line after fitting of LnN (epsilon) -Ln (1/epsilon) of each feeder line on a coordinate axis by taking LnN (epsilon) as a vertical coordinate and Ln (1/epsilon) as a horizontal coordinate;
and selecting the fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis.
Further, it is preferred that the transient zero sequence current i 0 (k) The calculation formula of (a) is as follows:
Figure BDA0002313869200000021
i A 、i B 、i C the method comprises the following steps of respectively representing three-phase currents, wherein k represents the number of a feeder line, and k =1,2 \8230; and n is the number of 8230; n is the total number of feeders.
Further, preferably, transient zero sequence current i in 1/4 period after fault is collected 0 The sampling rate was 10kHz.
Further, it is preferable that the fractal box dimension calculation is calculated using MATLAB fractal program.
Further, preferably, the specific method for selecting the faulty feeder line through the difference of the straight line fitted by each feeder line on the coordinate axis is as follows:
the distance between the straight lines after the fit of the sound feeder lines is far smaller than the distance between the straight lines after the fit of the sound feeder lines and the straight lines after the fit of the fault feeder lines.
The invention also provides a power distribution network fault line selection system based on the zero sequence current waveform fractal box dimension, which comprises the following steps:
the first processing module is used for acquiring transient zero-sequence current of each feeder line;
the second processing module is used for performing fractal box dimension calculation on the transient zero-sequence current of each feeder line;
the specific method for calculating the fractal box dimension comprises the following steps: taking a small box with the side length of epsilon, covering the transient zero sequence current to be measured by using the small box, wherein N (epsilon) represents the number of non-empty boxes during covering, and calculating the box dimension through epsilon and N (epsilon); then adjusting the side length of the small box, and carrying out box dimension calculation for multiple times;
drawing a straight line fitted by the LnN (epsilon) -LN (1/epsilon) of each feeder line on a coordinate axis by taking the LnN (epsilon) as a vertical coordinate and the LN (1/epsilon) as a horizontal coordinate;
and the fault line selection module selects the fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis.
The invention also provides electronic equipment which comprises a memory, a processor and a computer program which is stored on the memory and can run on the processor, wherein the processor executes the program to realize the steps of the power distribution network fault line selection method based on the zero-sequence current waveform fractal box dimension.
The present invention additionally provides a non-transitory computer readable storage medium having stored thereon a computer program which, when being executed by a processor, implements the steps of the above-mentioned power distribution network fault line selection method based on a zero-sequence current waveform fractal box dimension.
The principle of the invention is as follows: under the condition that a single-phase earth fault occurs in the power distribution network, the fractal box dimensions of the transient zero-sequence current of the fault feeder line and the transient zero-sequence current of the sound feeder line are obviously different on a two-dimensional plane. Based on the method, the transient zero-sequence current data of each feeder line under various fault conditions can be utilized, and the MATLAB fractal program is utilized to process the extracted transient zero-sequence current data, so that different areas of the fault feeder line and the sound feeder line box on a two-dimensional plane are obtained.
Compared with the prior art, the invention has the beneficial effects that:
1. the fault line selection is carried out by using the fractal box dimension difference of the transient zero sequence current curves of all the feeder lines when the fault occurs, so that the fault feeder line and the sound feeder line can be distinguished more obviously, the operation is simple and convenient, and the identification of the far-end high-resistance fault is greatly beneficial.
2. The method can clearly reflect the difference between the fault feeder line and the sound feeder line, and compared with other methods for distinguishing the fault feeder line from the non-fault feeder line, the method can more intuitively reflect the difference between the fault feeder line and the sound feeder line, so that the fault line can be selected out quickly.
Drawings
FIG. 1 is a block diagram of a power distribution network system of the present invention;
fig. 2 is a waveform diagram of each zero sequence current when the feeder L1 single-phase grounding transition resistance is 10 Ω in embodiment 1 of the present invention;
fig. 3 is a diagram of fault discrimination on a two-dimensional plane after fractal processing of each zero-sequence current curve in embodiment 1 of the present invention;
fig. 4 is a waveform diagram of each zero sequence current when the feeder L1 single-phase grounding transition resistance is 100 Ω in embodiment 2 of the present invention;
fig. 5 is a diagram of fault discrimination on a two-dimensional plane after fractal processing of each zero-sequence current curve in embodiment 2 of the present invention;
fig. 6 is a waveform diagram of each zero sequence current when the feeder L1 single-phase grounding transition resistance is 200 Ω in embodiment 3 of the present invention;
fig. 7 is a diagram of fault discrimination on a two-dimensional plane after fractal processing of each zero-sequence current curve in embodiment 3 of the present invention;
FIG. 8 is a schematic structural diagram of a power distribution network fault line selection system based on a zero-sequence current waveform fractal box dimension in the invention;
fig. 9 is a schematic structural diagram of an electronic device according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples.
It will be appreciated by those skilled in the art that the following examples are illustrative of the invention only and should not be taken as limiting the scope of the invention. Those skilled in the art will recognize that the specific techniques or conditions, not specified in the examples, are according to the techniques or conditions described in the literature of the art or according to the product specification. The materials or equipment used are not indicated by manufacturers, but are all conventional products available by purchase.
Arranging on a feeder line of a power distribution network along a line through electromagnetic transient simulationThe single-phase earth fault is used as a fault feeder line, and transient zero-sequence current i containing the fault feeder line and a plurality of healthy feeder lines is obtained at a protection installation position 0 (K)；
Figure BDA0002313869200000051
i A 、i B 、i C The method comprises the following steps of respectively representing three-phase currents, wherein k represents a mark number of a feeder line obtained at a protection installation position, and k =1,2 \8230;, n; n is the total number of feeders taken at the protection installation.
Preferably, transient zero sequence current i in a short-time window of 3ms is acquired 0 (the sampling rate is 10 kHz).
Then fractal processing is carried out on sample data of the zero-sequence current curve, and the specific method comprises the following steps: firstly, transient zero-sequence current data is found, the original transient zero-sequence current data is processed by an MATLAB fractal program, and the definition and formula of a fractal principle are as follows:
a small box with the side length of epsilon is taken and used for covering a body to be measured, some small boxes are empty due to various gaps in the body to be measured, N (epsilon) is the number of non-empty boxes, the size of the boxes is gradually reduced, and the obtained N (epsilon) is naturally increased. According to the above definition, a line after the fitting of LnN (epsilon) to Ln (1/epsilon) is drawn on the log-log coordinates (the invention is not limited to the fitting method), and the slope of the line is the box dimension D of the measured shape c Namely:
Figure BDA0002313869200000052
after the processing in the MATLAB fractal program, the box dimensions of the fault feeder and the sound feeder on a two-dimensional plane are obtained, and the fault feeder which is most obviously different from other feeders is the fault feeder.
As shown in fig. 8, a power distribution network fault line selection system based on a zero-sequence current waveform fractal box dimension includes:
the first processing module 101 is configured to acquire a transient zero-sequence current of each feeder line;
the second processing module 102 is configured to perform fractal box dimension calculation on the transient zero-sequence current of each feeder;
the specific method for calculating the fractal box dimension comprises the following steps: taking a small box with the side length of epsilon, covering the transient zero sequence current to be measured by using the small box, wherein N (epsilon) represents the number of non-empty boxes during covering, and calculating the box dimension through epsilon and N (epsilon); then adjusting the side length of the small box, and carrying out box dimension calculation for multiple times;
drawing a straight line after LnN (epsilon) -Ln (1/epsilon) fitting of each feeder line on a coordinate axis by taking LnN (epsilon) as a vertical coordinate and Ln (1/epsilon) as an abscissa;
and the fault line selection module 103 selects a fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis.
In the embodiment of the present invention, the first processing module 101 collects the transient zero sequence current of each feeder line; then, the second processing module 102 performs fractal box dimension calculation on the transient zero-sequence current of each feeder line; the specific method for calculating the fractal box dimension comprises the following steps: taking a small box with the side length of epsilon, covering the transient zero-sequence current to be measured by using the small box, wherein N (epsilon) represents the number of non-empty boxes during covering, and calculating the box dimension through epsilon and N (epsilon); then adjusting the side length of the small box, and carrying out box dimension calculation for multiple times; drawing a straight line after LnN (epsilon) -Ln (1/epsilon) fitting of each feeder line on a coordinate axis by taking LnN (epsilon) as a vertical coordinate and Ln (1/epsilon) as an abscissa; finally, the fault line selection module 103 selects a fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis.
The power distribution network fault line selection system based on the zero-sequence current waveform fractal box dimension can intuitively reflect the difference between a fault feeder line and a sound feeder line, so that a fault line can be selected quickly.
The system provided by the embodiment of the present invention is used for executing the above method embodiments, and for details of the process and the details, reference is made to the above embodiments, which are not described herein again.
Fig. 9 is a schematic structural diagram of an electronic device according to an embodiment of the present invention, and referring to fig. 9, the electronic device may include: a processor (processor) 201, a communication Interface (communication Interface) 202, a memory (memory) 203 and a communication bus 204, wherein the processor 201, the communication Interface 202 and the memory 203 complete communication with each other through the communication bus 204. The processor 201 may call logic instructions in the memory 203 to perform the following method: collecting transient zero-sequence current of each feeder line; performing fractal box dimension calculation on the transient zero-sequence current of each feeder line; the specific method for calculating the fractal box dimension comprises the following steps: taking a small box with the side length of epsilon, covering the transient zero-sequence current to be measured by using the small box, wherein N (epsilon) represents the number of non-empty boxes during covering, and calculating the box dimension through epsilon and N (epsilon); then adjusting the side length of the small box, and carrying out box dimension calculation for multiple times; drawing a straight line after LnN (epsilon) -Ln (1/epsilon) fitting of each feeder line on a coordinate axis by taking LnN (epsilon) as a vertical coordinate and Ln (1/epsilon) as an abscissa; and selecting the fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis.
In addition, the logic instructions in the memory 203 may be implemented in the form of software functional units and stored in a computer readable storage medium when the logic instructions are sold or used as independent products. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
In another aspect, an embodiment of the present invention further provides a non-transitory computer-readable storage medium, on which a computer program is stored, where the computer program is implemented by a processor to execute the method for fault line selection of a power distribution network based on a fractal box dimension of a zero-sequence current waveform provided in the foregoing embodiments, for example, the method includes: collecting transient zero sequence current of each feeder line; performing fractal box dimension calculation on the transient zero-sequence current of each feeder line; the specific method for calculating the fractal box dimension comprises the following steps: taking a small box with the side length of epsilon, covering the transient zero-sequence current to be measured by using the small box, wherein N (epsilon) represents the number of non-empty boxes during covering, and calculating the box dimension through epsilon and N (epsilon); then adjusting the side length of the small box, and carrying out box dimension calculation for multiple times; drawing a straight line after LnN (epsilon) -Ln (1/epsilon) fitting of each feeder line on a coordinate axis by taking LnN (epsilon) as a vertical coordinate and Ln (1/epsilon) as an abscissa; and selecting the fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis.
The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.
Examples of applications
Application example 1: a simulation model of a 110kV/35kV power distribution network is shown in figure 1, and the simulation model is provided with 3 feeders, and a neutral point of a transformer is grounded through an arc suppression coil series resistor. L is an arc suppression coil, and R is an arc suppression coil damping resistor. The feeder adopts three lines of an overhead line, an overhead-cable mixed line and a cable line, wherein the overhead feeder line L1=15km, the cable feeder line L2=6km and the cable mixed feeder line L3=17km. The load is selected from a constant power load model.
(1) A single-phase earth fault is arranged along a line of a feeder line L1 of a power distribution network, a 10 omega transition resistor is arranged, three-phase currents of three feeder lines are respectively obtained at the protection installation position as shown in figure 2, and a fault zero-sequence current i is calculated 0 。
(2) And extracting transient zero-sequence current data of each feeder line in a short time window of 3 ms.
(3) Fractal processing is carried out on the transient zero-sequence current curve data as shown in figure 3, and finally two-dimensional plane analysis is carried out to distinguish a fault feeder line and a sound feeder line by utilizing box dimension difference.
(4) Fault location: a single-phase earth fault occurs on an overhead line at a position 5km away from a bus by a feeder line L1; the starting time of the fault is 0.0418s; the sampling frequency was 10kHz.
Application example 2: a simulation model of a 110kV/35kV power distribution network is shown in figure 1, and the simulation model is provided with 3 feeders, and a neutral point of a transformer is grounded through an arc suppression coil series resistor. L is an arc suppression coil, and R is an arc suppression coil damping resistor. The feeder adopts three lines of an overhead line, an overhead-cable mixed line and a cable line, wherein the overhead feeder line L1=15km, the cable feeder line L2=6km and the cable mixed feeder line L3=17km. The load is selected from a constant power load model.
(1) A single-phase earth fault is arranged along a line of a feeder line L1 of a power distribution network, a transition resistor of 100 omega is arranged, three-phase currents of three feeder lines are respectively obtained at the protection installation position as shown in figure 4, and a fault zero-sequence current i is calculated 0 。
(2) And extracting transient zero-sequence current data of each feeder line in a short time window of 3 ms.
(3) Fractal processing is carried out on the transient zero-sequence current curve data as shown in fig. 5, and finally two-dimensional plane analysis is carried out to distinguish a fault feeder line and a sound feeder line by utilizing box dimension difference.
(4) Fault location: a single-phase earth fault occurs on an overhead line at a distance of 6km from a bus to a feeder line L1; the starting time of the fault is 0.0418s; the sampling frequency was 10kHz.
Application example 3: a simulation model of a 110kV/35kV power distribution network is shown in figure 1, and the simulation model is provided with 3 feeders, and a neutral point of a transformer is grounded through an arc suppression coil series resistor. L is an arc suppression coil, and R is an arc suppression coil damping resistor. The feeder line adopts three lines of an overhead line, an overhead-cable mixed line and a cable line, wherein the overhead feeder line L1=15km, the cable feeder line L2=6km and the cable mixed feeder line L3=17km. The load is selected from a constant power load model.
(1) A single-phase earth fault is arranged along a line of a feeder line L1 of a power distribution network, a transition resistor of 200 omega is arranged, three-phase currents of three feeder lines are respectively obtained at the protection installation position as shown in figure 6, and a fault zero-sequence current i is calculated 0 。
(2) And extracting transient zero sequence current data of each feeder line in a short time window of 3 ms.
(3) Fractal processing is carried out on the transient zero-sequence current curve data as shown in fig. 7, and finally two-dimensional plane analysis is carried out to distinguish a fault feeder line and a sound feeder line by utilizing box dimension difference.
(4) Fault location: a single-phase earth fault occurs on an overhead line at a position 4km away from a bus by a feeder line L1; the starting time of the fault is 0.0418s; the sampling frequency was 10kHz.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (4)

1. The power distribution network fault line selection method based on the zero-sequence current waveform fractal box dimension is characterized by comprising the following steps of:
collecting transient zero-sequence current of each feeder line;
performing fractal box dimension calculation on the transient zero-sequence current of each feeder line;
the specific method for calculating the fractal box dimension comprises the following steps: taking a small box with the side length of epsilon, covering the transient zero-sequence current to be measured by the small box,
Figure DEST_PATH_IMAGE001
representing the number of non-empty boxes in the covering, by ε and
Figure 996960DEST_PATH_IMAGE001
calculating a box dimension; then adjusting the side length of the small box, and carrying out box dimension calculation for multiple times;
to be provided with
Figure 462577DEST_PATH_IMAGE002
As a vertical coordinate, with
Figure DEST_PATH_IMAGE003
Plotting each feeder line as an abscissa, on a coordinate axis
Figure 596886DEST_PATH_IMAGE002
~
Figure 882374DEST_PATH_IMAGE003
A straight line after fitting;
selecting a fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis;
transient zero sequence current
Figure 25910DEST_PATH_IMAGE004
The calculation formula of (a) is as follows:
Figure 346033DEST_PATH_IMAGE006
i A 、i B 、i C respectively represent the three-phase current, respectively,kthe reference numerals indicating the feed lines are used,k=1,2 \ 8230 \ 8230, n; n is the total number of the feeder lines;
the specific method for selecting the fault feeder line through the difference of the straight line fitted by each feeder line on the coordinate axis comprises the following steps:
the distance between the straight lines after fitting of the sound feeder lines is far smaller than the distance between the straight lines after fitting of the sound feeder lines and the straight lines after fitting of the fault feeder lines;
after collecting fault
Figure DEST_PATH_IMAGE007
Transient zero sequence current in cyclei 0 The sampling rate is 10kHz;
the fractal box dimension calculation was calculated using the MATLAB fractal program.
2. Distribution network fault route selection system based on zero sequence current waveform fractal box dimension includes:
the first processing module is used for acquiring transient zero-sequence current of each feeder line;
transient zero sequence current
Figure 916823DEST_PATH_IMAGE008
The calculation formula of (a) is as follows:
Figure 689607DEST_PATH_IMAGE006
i A 、i B 、i C respectively represent the three-phase current, respectively,kthe reference numerals indicating the feed lines are used,k=1,2 \ 8230\8230; n is the total number of the feeder lines;
after collecting fault
Figure 636834DEST_PATH_IMAGE007
Transient zero sequence current in cyclei 0 At a sampling rate of10kHz；
The second processing module is used for performing fractal box dimension calculation on the transient zero-sequence current of each feeder line;
the specific method for calculating the fractal box dimension comprises the following steps: taking a small box with the side length of epsilon, covering the transient zero-sequence current to be measured by the small box,
Figure DEST_PATH_IMAGE009
representing the number of non-empty boxes in the covering, by ε and
Figure 545884DEST_PATH_IMAGE009
calculating a box dimension; then adjusting the side length of the small box, and carrying out box dimension calculation for multiple times;
to be provided with
Figure 287575DEST_PATH_IMAGE010
As a vertical coordinate, with
Figure DEST_PATH_IMAGE011
Plotting each feeder line as an abscissa, on a coordinate axis
Figure 547655DEST_PATH_IMAGE010
~
Figure 32995DEST_PATH_IMAGE011
A straight line after fitting;
calculating the fractal box dimension by using an MATLAB fractal program;
the fault line selection module selects a fault feeder line according to the difference of the straight line fitted by each feeder line on the coordinate axis;
the specific method for selecting the fault feeder line through the difference of the straight line fitted by each feeder line on the coordinate axis comprises the following steps:
the distance between the straight lines after the fit of each sound feeder line is far smaller than the distance between the straight lines after the fit of the sound feeder lines and the straight lines after the fit of the fault feeder lines.
3. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor when executing the program implements the steps of the method for fault line selection for a power distribution network based on zero-sequence current waveform fractal box dimension as claimed in claim 1.
4. A non-transitory computer readable storage medium, on which a computer program is stored, wherein the computer program, when being executed by a processor, implements the steps of the method for fault line selection for a power distribution network based on zero sequence current waveform fractal box dimension as claimed in claim 1.
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