CN112067948A - Fault line selection method, system and terminal for single-phase earth fault of power distribution network and readable storage medium - Google Patents
Fault line selection method, system and terminal for single-phase earth fault of power distribution network and readable storage medium Download PDFInfo
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Abstract
The invention discloses a fault line selection method, a system, a terminal and a readable storage medium for single-phase earth faults of a power distribution network, wherein the method comprises the following steps: s1: after the single-phase earth fault occurs to the power distribution network, a voltage source is connected to a neutral point; s2: acquiring zero sequence current of each feeder line of the power distribution network in real time to obtain a zero sequence current sequence of each feeder line; s3: for each feeder line, selecting the length of a zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line, wherein the length of the small window is half of a power frequency period; s4: identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder. The method provided by the invention can amplify the fault characteristics so as to reliably identify the fault line, and in addition, the method can also be suitable for the working condition of the single-phase high-resistance earth fault.
Description
Technical Field
The invention belongs to the technical field of power distribution network fault detection, and particularly relates to a fault line selection method, a fault line selection system, a fault line selection terminal and a readable storage medium for a single-phase earth fault of a power distribution network.
Background
The neutral point of the power distribution network in China mainly adopts an ungrounded mode and an arc suppression coil grounding mode, when a single-phase grounding fault occurs in the power distribution network, the neutral point is not effectively grounded, the voltage level is low, the fault current is weak, the fault characteristics are not obvious, the fault line selection is difficult to accurately realize, and the fault section cannot be reliably cut. The system with fault operation may change the fault property, enlarge the fault range, seriously threaten the public property and personal safety, and the longer the operation time with fault, the larger the hazard. According to statistics, the loss caused by the faults of the power distribution network is up to hundreds of billions of yuan every year, and the death number caused by the electric shock accidents of the power distribution network accounts for about 10 percent of the death number of other accidents. Therefore, the single-phase earth fault line selection research of the power distribution network has important significance in the aspects of quickly determining a fault area, reducing economic and property losses, guaranteeing equipment and personal safety and the like.
The fault line selection method can be roughly divided into two aspects: a passive line selection method and an active line selection method. The passive line selection refers to line selection by using an electric signal measured by a mutual inductor after a fault, and the passive line selection methods which are researched more include a group ratio amplitude phase comparison method, a transient power method, an intelligent algorithm, a fusion algorithm and the like. The group amplitude-to-phase ratio method identifies the fault line by comparing the transient amplitude and the phase of the zero sequence current of each feeder line, has higher accuracy and is easily influenced by noise interference and sampling frequency; the transient power method realizes fault line selection by utilizing transient active components, is suitable for single-phase earth faults with higher transition resistance, but has lower sensitivity in low-resistance faults; the intelligent algorithm generally does not start from a fault characteristic mechanism, and is difficult to mine the intrinsic fault attribute; the fused line selection method combines the advantages of different methods to realize fault line selection, but the switching limit of the line selection method needs to be verified, and the fused quality needs to be examined.
And the active line selection means that the fault line selection is realized by actively injecting signals or actively adjusting electrical equipment and the like after the fault. There are several active route selection methods that are more studied: injection signal method, arc suppression coil adjustment method, medium resistance method, and the like. The existing signal injection method has small additional signal and low reliability; the arc suppression coil adjustment method generally realizes fault line selection through the mutation before and after arc suppression coil adjustment, but the fault characteristics under high-resistance fault are weaker; the middle resistance method is used for distinguishing a fault line by adding active components into a resistor after a fault, and the line selection accuracy is high.
When the single-phase earth fault of the power distribution network, particularly when the single-phase earth fault of the power distribution network occurs, the feeder current has no obvious fault characteristics, the traditional passive line selection relying on the fault information of the power distribution network is difficult to reliably identify a fault line, and the artificial manufacture or amplification of the fault characteristics through active signal injection provides a new idea for the high-resistance earth fault line selection of the power distribution network, so that how to realize the high-resistance earth fault line selection method of the power distribution network needs further research.
Disclosure of Invention
The invention aims to provide a fault line selection method for single-phase earth faults of a power distribution network, which can reliably identify fault lines, is simple to implement and strong in adaptability, and is particularly suitable for the working condition of single-phase high-resistance earth faults.
The invention provides a fault line selection method for single-phase earth faults of a power distribution network, which comprises the following steps:
s1: after the single-phase earth fault occurs to the power distribution network, a voltage source is connected to a neutral point;
s2: acquiring zero sequence current of each feeder line of the power distribution network in real time to obtain a zero sequence current sequence of each feeder line;
sampling three-phase currents of outgoing lines on each feeder line of the power distribution network in real time to obtain three-phase current sampling sequences of each feeder line, and synthesizing zero-sequence currents of each feeder line by the three-phase current sampling sequences;
s3: for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line;
wherein, theLength T of small windowsSatisfies the following conditions: t issIf the high-frequency harmonic frequency M of a voltage source connected to the neutral point is an odd number,
if the high frequency harmonic number M of the voltage source counted by the neutral point is even,
m can be evenly divided by beta and beta is not equal to M;
s4: identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
The invention is based on the research that the fault line contains power frequency and frequency multiplication components, while the sound line only contains frequency multiplication components, therefore, the fault characteristics are amplified by summing the zero sequence current of the small window, and simultaneously, the sum value of the zero sequence current in more small windows is obtained by moving the step length, and more comparison data are further obtained, so that the fault line and the sound line can be amplified or identified more intuitively. Meanwhile, the voltage of a fault point is actively regulated and controlled through a voltage source connected to a neutral point of the power distribution network, so that the enhancement and amplification of fault characteristics are realized, and further fault line selection is realized.
Further preferably, the preset step length is 1, the length of the small window is half power frequency period, and the cumulative summation sequence of the kth feeder line is as follows:
in the formula, Sk0The accumulated summation sequence of the kth feeder is represented, N is a sampling point in a power frequency period, Ns is the number of sampling points in the zero sequence current sequence with the selected length, ik0(n)、ik0(n+1)、ik0(n+2)、ik0(N + Ns-N/2) respectively represents the zero sequence current corresponding to the sampling points at the nth length, the nth +1 length, the nth +2 length and the nth + Ns-N/2 length in the zero sequence current sequence of the kth feeder line, Sk0(1)、Sk0(2)、Sk0(p)、Sk0(Ns-N/2+1) respectively represents the summation value of the zero sequence current in the 1 st, 2 nd, p th and Ns-N/2+1 th small windows in the accumulated summation sequence of the kth feeder line.
Further preferably, the implementation process of step S4 is: and calculating the root mean square value of each feeder line, comparing the root mean square value with a threshold value, if the root mean square value is larger than the threshold value, determining the corresponding feeder line as a fault line, and otherwise, determining the corresponding feeder line as a sound line.
Further preferably, the root mean square value of the k-th feeder line is as follows:
in the formula, SkRepresenting the root mean square value, S, of the k-th feederk0And (p) the summation value of the zero sequence currents in the pth small window of the kth feeder line is represented, Ns is the number of sampling points in the zero sequence current sequence with the selected length, and N is the sampling point in a power frequency period.
Further preferably, the calculation formula of the threshold is as follows:
in the formula, SsetDenotes a threshold value, SkAnd the root mean square value of the kth feeder line is shown, and m is the total number of the feeder lines.
Further preferably, the voltage source connected in step S1 is a frequency doubling voltage source, and the amplitude U of the frequency doubling voltage sourcezSatisfies the following conditions: KUp<Uz<UpFrequency fzSatisfy fz＝Mf0Wherein, K is a reliable coefficient, and the value range is as follows: [0.15,0.2]，f0M is a positive integer greater than or equal to 2 for the system fundamental frequency.
Further preferably, the zero-sequence current collected in step S2 is at least data of the beginning of the third power frequency cycle after the fault.
In a second aspect, the present invention further provides a system based on the method, wherein after a single-phase ground fault occurs in a power distribution network, a voltage source is connected to a neutral point, and the system includes:
a zero sequence current sequence acquisition module: acquiring zero sequence current of each feeder line of the power distribution network in real time to obtain a zero sequence current sequence of each feeder line;
an accumulation summation sequence acquisition module: for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line;
an authentication module: identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
In a third aspect, the present invention further provides a terminal, including a processor and a memory, where the memory stores a computer program, and the processor calls the computer program to execute:
the method comprises the steps that after a single-phase earth fault occurs in a power distribution network and a voltage source is connected to a neutral point, zero sequence current of each feeder line of the power distribution network is obtained in real time to obtain a zero sequence current sequence of each feeder line; for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line; and identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
In a fourth aspect, the present invention also provides a readable storage medium storing a computer program, the computer program being invoked to perform:
the method comprises the steps that after a single-phase earth fault occurs in a power distribution network and a voltage source is connected to a neutral point, zero sequence current of each feeder line of the power distribution network is obtained in real time to obtain a zero sequence current sequence of each feeder line; for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line; and identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
Advantageous effects
1. According to the fault line selection method for the single-phase earth fault of the power distribution network, on one hand, the voltage of a fault point is actively regulated and controlled through a voltage source connected to a neutral point of the power distribution network, so that the enhancement and amplification of fault characteristics are realized, and further the fault line selection is realized; in the invention, the zero sequence current summation frequency multiplication component in a small window with a set length is theoretically 0, the power frequency component is far larger than 0, the characteristic difference between a fault line and a sound line is further enlarged, and simultaneously, the summation values of the zero sequence current in more small windows are obtained by moving step length, so that more comparison data are further obtained, and the fault line and the sound line are enlarged or identified more intuitively.
2. The fault characteristics extracted by the method are accumulated summation of signals, the difference between a fault line and a sound line can be enlarged in the accumulation process, and the fault identification characteristics can be increased by connecting a voltage source to a neutral point to increase the amplitude of the voltage source, so that the method provided by the invention can be suitable for single-phase faults of a high-resistance grounded power distribution network with weak fault characteristics, and the reliability and the applicability are further improved.
Drawings
Fig. 1 is a diagram of a simulation model of a power distribution network according to an embodiment of the present invention.
Fig. 2 is a zero-sequence equivalent circuit diagram of a power distribution network simulation model provided by the embodiment of the invention.
Fig. 3 is a waveform diagram of a zero sequence current sequence provided by an embodiment of the present invention.
FIG. 4 is a cumulative summing sequence S according to an embodiment of the present invention10(n)～S50(n) waveform diagrams.
Detailed Description
The invention provides a fault line selection method for a single-phase earth fault of a power distribution network, which is used for realizing the identification of a fault line, wherein the method comprises the following steps:
s1: and after the single-phase earth fault occurs in the power distribution network, a voltage source is connected to a neutral point. Preferably, the amplitude and the frequency of the neutral point are respectively UzAnd ωzWith an initial phase of
And the amplitude satisfies：KUp<Uz<UpFrequency fzSatisfy fz＝Mf0Wherein, K is a reliable coefficient, and the value range is as follows: [0.15,0.2]，f0The system fundamental frequency is M, the high frequency harmonic frequency is M, and the value is an integer greater than or equal to 2.
S2: and acquiring the zero sequence current of each feeder line of the power distribution network in real time to obtain the zero sequence current sequence of each feeder line. Wherein, gather each feeder three-phase current in real time, obtain each feeder three-phase current sampling sequence, for example the kth feeder: i.e. ikA(n)、ikB(n)、ikC(n), wherein k is 1,2, …, m, m is the number of outgoing lines of the feeder line; then the formula ik0(n)＝ikA(n)+ikB(n)+ikC(n) synthesizing each feeder zero sequence current sequence ik0(n), wherein n is a sampling point.
S3: for each feeder line, the length of the zero sequence current sequence is selected, and the small window is moved by a preset step length and the zero sequence currents in the small window are summed to obtain an accumulated summation sequence of each feeder line, for example, in this embodiment, the frequency doubling voltage source is a voltage source with a frequency of 100Hz, and the length of the small window is set to be half of the power frequency period. The invention is not so limited, however, as the length T of the small windowsSatisfies the following conditions: t issIf the high-frequency harmonic frequency M of a voltage source connected to the neutral point is an odd number,
if the high frequency harmonic number M of the voltage source counted by the neutral point is even,
m can be evenly divided by β, β is a positive integer and β ≠ M. For example, if M is 3, the length of the small window is 1/3 power frequency cycles; if M is 4, the length of the small window is 1/2 or 1/4 power frequency cycles; if M is 6, the length of the small window is 1/2 or 1/3 or 1/6 power frequency cycles.
For example, taking the preset step size of 1, 1/2 power frequency cycles and the length of the selected zero sequence of 5 power frequency cycles as an example, that is, 5T, where T is the power frequency cycle, the cumulative summation sequence of the kth feeder is as follows:
in the formula, Sk0The accumulated summation sequence of the kth feeder is represented, N is a sampling point in a power frequency period, Ns is the number of sampling points in the zero sequence current sequence with the selected length, ik0(n)、ik0(n+1)、ik0(n+2)、ik0(N + Ns-N/2) respectively represents the zero sequence current corresponding to the sampling points at the nth length, the nth +1 length, the nth +2 length and the nth + Ns-N/2 length in the zero sequence current sequence of the kth feeder line, Sk0(1)、Sk0(2)、Sk0(p)、Sk0(Ns-N/2+1) respectively represents the summation value of the zero sequence current in the 1 st, 2 nd, p th and Ns-N/2+1 th small windows in the accumulated summation sequence of the kth feeder line.
S4: identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder. Preferably, the root mean square value of each feeder line is calculated and compared with a threshold, if the root mean square value is greater than the threshold, the corresponding feeder line is a fault line, otherwise, the corresponding feeder line is a sound line, and the root mean square value formula and the threshold formula are as follows:
in the formula, SkRoot mean square value representing k-th feeder
In the formula, SsetRepresenting a threshold value.
In other possible embodiments, considering the difference between the faulty line and the healthy line, the abnormal line can be identified by other means according to the accumulated summation sequence of the feeder lines, such as: the means of the average value, the maximum value, the curve chart of the accumulation summation sequence and the like of accumulation summation can identify abnormal lines.
The invention will be further described with reference to an application example.
As shown in attached figure 1, the power distribution network applying the method of the invention is a 10kV single-ended power supply radial simulation model, 5 feeder lines are provided in the figure, the lengths of the feeder lines are respectively 10km, 20km, 10km, 19km and 6km, wherein the feeder lines 1 and 2 are overhead-cable mixed lines, the feeder lines 3 and 4 are overhead lines, and the feeder line 5 is a cable line. The system neutral point is grounded through a grounding transformer and an arc suppression coil, and 8% overcompensation is set in simulation, Lp、RpArc suppression coils and their series resistances of 10 omega and 0.4742H, E, respectivelyzFrequency multiplication voltage source, U, for connecting to neutral point of distribution networkzAnd ωzThe amplitude and the angular frequency of the frequency doubling voltage source are respectively. Assuming that a single-phase ground fault occurs in the feeder 5, the transition resistance is 800 Ω.
For simplicity, the line parameters in the embodiment are set to be the same, and the specific line parameters are as follows:
overhead line:
the positive sequence resistance, the inductance and the capacitance are respectively as follows: r is1＝0.178Ω/km、l1＝1.21mH/km、c1＝0.012uF/km；
The zero sequence resistance, the inductance and the capacitance are respectively as follows: r is0＝0.25Ω/km、l0＝5.54mH/km、c0＝0.006uF/km。
Cable lines:
the positive sequence resistance, the inductance and the capacitance are respectively as follows: r is1＝0.27Ω/km、l1＝0.255mH/km、c1＝0.379uF/km；
The zero sequence resistance, the inductance and the capacitance are respectively as follows: r is0＝2.7Ω/km、l0＝1.109mH/km、c0＝0.276uF/km。
The specific steps of the embodiment are as follows:
the zero sequence equivalent circuit diagram of the simulation model shown in fig. 1 is shown in fig. 2. The zero sequence current of the fault line can be known by applying the superposition principle of the graphs
Zero sequence current of sound circuit
As shown in the following formula:
in the formula (I), the compound is shown in the specification,
is the fault point voltage, RfIs a fault point transition resistance. From the above formula, the zero sequence current of the fault line includes the power frequency component and the frequency multiplication component of the access voltage source, and the healthy line only includes the frequency multiplication component of the access voltage source, so that the fault characteristics with significant difference can be formed.
According to the formula, the fault line comprises power frequency and frequency multiplication components, and the healthy line only comprises the frequency multiplication component, so that half power frequency period summation is carried out, the frequency multiplication components are 0, the power frequency components are far larger than 0, and the accumulated summation can further enlarge the characteristic difference between the fault line and the healthy line after 1 step length is moved.
1) After the feeder line 5 has a single-phase earth fault, a frequency multiplication voltage source is connected to a neutral point of the power distribution network immediately, and in the embodiment, the amplitude, the angular frequency and the initial phase angle of the connected voltage source are 3000V, 400 pi and 45 degrees respectively.
2) Further, sampling the three-phase current on each feeder line in real time at a sampling frequency of 5kHz to obtain a three-phase current sampling sequence i of each feeder linekA(n)、ikB(n)、ikC(n), wherein k is 1,2, …,5, represented by formula ik0(n)＝ikA(n)+ikB(n)+ikC(n) synthesizing each feeder zero sequence current ik0(n), the obtained zero sequence current sequence waveform is shown in figure 3.
3) Further, press
For 5 feedersAnd accumulating and summing the zero-sequence currents of the line in a half power frequency period to obtain corresponding values of 5 feeder lines: 0.1583, -1.8922, 0.0209, 0.3654, -133.43.
4) Further, the length of the data window is selected to be 5T, T is the fundamental frequency period, and the accumulated summation sequence S of each feeder line is obtained according to the formula (2)10(n)～S50The waveforms of (n) are shown in FIG. 4.
5) Further, calculate S10(n)～S50Root mean square value S of (n)1～S50.2401, 0.7929, 1.2899, 0.4483 and 226.18 respectively, and the setting threshold S of the fault line selection is calculated by the formula (4)set45.791, it is obvious that only S5>SsetTherefore, the feeder 5 is selected as the fault line, and the line selection result is correct.
In some examples, the present invention further provides a system of a fault line selection method based on a single-phase ground fault of a power distribution network, wherein a voltage source is connected to a neutral point after the single-phase ground fault occurs in the power distribution network, and the system includes:
a zero sequence current sequence acquisition module: acquiring zero sequence current of each feeder line of the power distribution network in real time to obtain a zero sequence current sequence of each feeder line;
an accumulation summation sequence acquisition module: for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line;
an authentication module: identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
It should be understood that, the specific implementation process of the above unit module refers to the method content, and the present invention is not described herein in detail, and the division of the above functional module unit is only a division of a logic function, and there may be another division manner in the actual implementation, for example, multiple units or components may be combined or may be integrated into another system, or some features may be omitted, or may not be executed. Meanwhile, the integrated unit can be realized in a hardware form, and can also be realized in a software functional unit form.
In some examples, the present invention also provides a terminal comprising a processor and a memory, the memory storing a computer program, the processor calling the computer program to perform:
the method comprises the steps that after a single-phase earth fault occurs in a power distribution network and a voltage source is connected to a neutral point, zero sequence current of each feeder line of the power distribution network is obtained in real time to obtain a zero sequence current sequence of each feeder line; for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line; and identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
In some examples, the invention also provides a readable storage medium storing a computer program that is invoked to perform:
the method comprises the steps that after a single-phase earth fault occurs in a power distribution network and a voltage source is connected to a neutral point, zero sequence current of each feeder line of the power distribution network is obtained in real time to obtain a zero sequence current sequence of each feeder line; for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line; and identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
It should be understood that in the embodiments of the present invention, the Processor may be a Central Processing Unit (CPU), and the Processor may also be other general purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other Programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The memory may include both read-only memory and random access memory, and provides instructions and data to the processor. The portion of memory may also include non-volatile random access memory. For example, the memory may also store device type information.
The readable storage medium is a computer readable storage medium, which may be an internal storage unit of the controller according to any of the foregoing embodiments, for example, a hard disk or a memory of the controller. The readable storage medium may also be an external storage device of the controller, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), and the like provided on the controller. Further, the readable storage medium may also include both an internal storage unit of the controller and an external storage device. The readable storage medium is used for storing the computer program and other programs and data required by the controller. The readable storage medium may also be used to temporarily store data that has been output or is to be output. It should be emphasized that the examples described herein are illustrative and not restrictive, and thus the invention is not to be limited to the examples described herein, but rather to other embodiments that may be devised by those skilled in the art based on the teachings herein, and that various modifications, alterations, and substitutions are possible without departing from the spirit and scope of the present invention.
Claims (10)
1. A fault line selection method for a single-phase earth fault of a power distribution network is characterized by comprising the following steps: the method comprises the following steps:
s1: after the single-phase earth fault occurs to the power distribution network, a voltage source is connected to a neutral point;
s2: acquiring zero sequence current of each feeder line of the power distribution network in real time to obtain a zero sequence current sequence of each feeder line;
s3: for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line;
wherein the length T of the small windowsSatisfies the following conditions: t issIf the high-frequency harmonic frequency M of a voltage source connected to the neutral point is an odd number,
if the high frequency harmonic number M of the voltage source counted by the neutral point is even,
m can be evenly divided by beta, beta is a positive integer and beta is not equal to M;
s4: identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
2. The method of claim 1, wherein: the preset step length is 1, the length of the small window is half power frequency period, and the cumulative summation sequence of the kth feeder line is as follows:
in the formula, Sk0The accumulated summation sequence of the kth feeder is represented, N is a sampling point in a power frequency period, Ns is the number of sampling points in the zero sequence current sequence with the selected length, ik0(n)、ik0(n+1)、ik0(n+2)、ik0(N + Ns-N/2) respectively represents the zero sequence current corresponding to the sampling points at the nth length, the nth +1 length, the nth +2 length and the nth + Ns-N/2 length in the zero sequence current sequence of the kth feeder line, Sk0(1)、Sk0(2)、Sk0(p)、Sk0(Ns-N/2+1) respectively represents the summation value of the zero sequence current in the 1 st, 2 nd, p th and Ns-N/2+1 th small windows in the accumulated summation sequence of the kth feeder line.
3. The method of claim 1, wherein: the implementation process of step S4 is: and calculating the root mean square value of each feeder line, comparing the root mean square value with a threshold value, if the root mean square value is larger than the threshold value, determining the corresponding feeder line as a fault line, and otherwise, determining the corresponding feeder line as a sound line.
4. The method of claim 3, wherein: the root mean square value of the k-th feeder line is as follows:
in the formula, SkRepresenting the root mean square value, S, of the k-th feederk0And (p) the summation value of the zero sequence currents in the pth small window of the kth feeder line is represented, Ns is the number of sampling points in the zero sequence current sequence with the selected length, and N is the sampling point in a power frequency period.
5. The method of claim 3, wherein: the calculation formula of the threshold is as follows:
in the formula, SsetDenotes a threshold value, SkAnd the root mean square value of the kth feeder line is shown, and m is the total number of the feeder lines.
6. The method of claim 1, wherein: the voltage source accessed in the step S1 is a frequency doubling voltage source, and the amplitude U of the frequency doubling voltage sourcezSatisfies the following conditions: KUp<Uz<UpFrequency fzSatisfy fz＝Mf0Wherein, K is a reliable coefficient, and the value range is as follows: [0.15,0.2]，f0M is a positive integer greater than or equal to 2 for the system fundamental frequency.
7. The method of claim 1, wherein: the zero-sequence current collected in step S2 is at least data from the beginning of the third power frequency cycle after the fault.
8. A system based on the method of any one of claims 1-7, characterized by: after a single-phase ground fault occurs in a power distribution network, a voltage source is connected to a neutral point, and the system comprises:
a zero sequence current sequence acquisition module: acquiring zero sequence current of each feeder line of the power distribution network in real time to obtain a zero sequence current sequence of each feeder line;
an accumulation summation sequence acquisition module: for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line;
an authentication module: identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
9. A terminal, characterized by: comprising a processor and a memory, the memory storing a computer program that the processor calls to perform:
the method comprises the steps that after a single-phase earth fault occurs in a power distribution network and a voltage source is connected to a neutral point, zero sequence current of each feeder line of the power distribution network is obtained in real time to obtain a zero sequence current sequence of each feeder line; for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line; and identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
10. A readable storage medium, characterized by: a computer program is stored, the computer program being invoked to perform:
the method comprises the steps that after a single-phase earth fault occurs in a power distribution network and a voltage source is connected to a neutral point, zero sequence current of each feeder line of the power distribution network is obtained in real time to obtain a zero sequence current sequence of each feeder line; for each feeder line, selecting the length of the zero sequence current sequence, moving a small window by a preset step length, and summing the zero sequence currents in the small window to obtain an accumulated summation sequence of each feeder line; and identifying whether the feeder is faulty or healthy based on the accumulated sum sequence for each feeder.
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