Power distribution network grounding fault line selection method, system, medium and equipment

Abstract

The invention discloses a power distribution network grounding fault line selection method, system, medium and equipment, and the method comprises the steps: injecting a current signal with a preset characteristic frequency into a power distribution network from a neutral point; collecting a current signal corresponding to the predetermined characteristic frequency in the three-phase current of each line of the power distribution network by taking the characteristic signal period as a time window length; calculating the zero-sequence current of each line of the power distribution network under the preset characteristic frequency; calculating the quadratic sum of the zero-sequence current in each time window to represent the energy of the zero-sequence current in one period; calculating the time sequence energy ratio of each line according to the ratio of the energy of the adjacent time windows so as to represent the change of the zero sequence current energy of the line along with time; performing pairwise ratio calculation on the time sequence energy ratios of different lines, and constructing an energy change synchronization matrix; and continuously monitoring the energy change synchronism matrix, and when a certain line is asynchronous in change relative to other lines, has fixed characteristics and is synchronous in change with other lines, considering that the line has a ground fault.

Description

Technical Field

[0001] The present invention relates to the technical field of grounding faults in distribution networks, and in particular to a method, system, medium and equipment for selecting a grounding fault line in a distribution network. Background Art

[0002] Ground faults are a common and potentially harmful fault in distribution network operations, particularly in systems where the neutral point is ungrounded or grounded via arc suppression coils. Ground faults can not only damage equipment and cause electrical fires, but also threaten system stability and personal safety.

[0003] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0004] The present invention provides a method, system, medium and equipment for selecting a line for a ground fault in a distribution network. A current signal of a characteristic frequency is injected into the distribution network from a neutral point, a magnetoelectric coupling sensor is used to collect the zero-sequence current of the corresponding characteristic frequency in the line, and a zero-sequence current energy change synchronization matrix between different lines is calculated. By comparing the differences in zero-sequence current energy synchronization between different lines, the line where a ground fault occurs in the system can be accurately identified, thereby realizing ground fault line selection in the distribution network.

[0005] A method for selecting a ground fault line in a distribution network includes:

[0006] Injecting a current signal of a predetermined characteristic frequency into the distribution network from the neutral point;

[0007] The current signal corresponding to the predetermined characteristic frequency in the three-phase current of each line of the distribution network is collected using the characteristic signal period as the time window length;

[0008] Calculating the zero-sequence current of each line of the distribution network at the predetermined characteristic frequency;

[0009] The square sum of the zero-sequence current in each time window is calculated to represent the energy of the zero-sequence current in one cycle;

[0010] The time sequence energy ratio of each line is calculated based on the ratio of the energy in adjacent time windows to characterize the change of the line zero sequence current energy over time;

[0011] Perform pairwise ratio calculations on the time series energy ratios of different lines to construct an energy change synchronization matrix;

[0012] The energy change synchronization matrix is ​​continuously monitored. When a line changes asynchronously with respect to other lines and shows a fixed feature, while other lines change synchronously with each other, it is considered that a ground fault occurs in the line.

[0013] In the method for selecting a ground fault line in a distribution network, the predetermined characteristic frequency avoids the power frequency harmonics of the distribution network, and the signal injection mode is a constant current source.

[0014] In the distribution network ground fault line selection method, a magnetoelectric coupling sensor is used to collect the current signal corresponding to the predetermined characteristic frequency from the three-phase current of each line. The operating frequency of the magnetoelectric coupling sensor is adjusted to the same characteristic frequency as the injected signal. The magnetoelectric coupling sensor has a frequency-selective characteristic and is more sensitive to signals at the operating frequency.

[0015] In the method for selecting a ground fault line in a distribution network, the zero-sequence current of each line in the distribution network at the predetermined characteristic frequency is calculated. (1)

[0016] where i k is the zero-sequence current of the kth line, k=1,2,3,4……, i k,a 、i k,b 、i k,c are the currents of phases a, b, and c of the kth line respectively.

[0017] In the method for selecting a ground fault line in a distribution network, the square sum of zero-sequence currents E in a time window is calculated. k [m], as shown in formula (2)

[0018] (2)

[0019] Among them, T n is the number of sampling points corresponding to one cycle length at a fixed sampling frequency, m is the time window number, t m is the starting position of the current signal corresponding to the mth time window, i k [t m +n] indicates that the kth line is at t m Zero sequence current at +n.

[0020] In the distribution network ground fault line selection method, the zero-sequence current time sequence energy ratio is calculated as shown in formula (3):

[0021] (3)

[0022] where r k [m] represents the zero-sequence current time sequence energy ratio at the mth time window, r k The value of [m] is always greater than 0.

[0023] In the distribution network ground fault line selection method, the energy change synchronization matrix calculation formula is as shown in formula (4):

[0024] (4)

[0025] where a i,j [m] is the energy change synchronization coefficient of the i-th line and the j-th line in the m-th time window, a i,j The value of [m] is always greater than 0. When i=j, a i,j [m]=1, if i≠j, when a i,j [m]=1, the energy changes of the i-th line and the j-th line are completely synchronized. i,j [m]>1, the energy of the i-th line increases compared to the j-th line. The larger the value, the greater the increase. When a i,j [m]<1, the energy of the i-th line is reduced compared to the j-th line. The closer the value is to 0, the greater the reduction.

[0026] A system for implementing the method includes:

[0027] A signal injection module, used for injecting a current signal of a predetermined characteristic frequency into the neutral point;

[0028] The magnetoelectric coupling sensor array adapts to the predetermined characteristic frequency to collect the three-phase current of each line;

[0029] a calculation unit, which calculates the zero-sequence current of each line of the distribution network at the predetermined characteristic frequency, calculates the sum of the squares of the zero-sequence current in each time window to characterize the energy of the zero-sequence current in one cycle, and calculates the time-sequence energy ratio of each line based on the ratio of the energies of adjacent time windows to characterize the change of the zero-sequence current energy of the line over time;

[0030] A construction unit, which performs pairwise ratio calculations on the time series energy ratios of different lines to construct an energy change synchronization matrix;

[0031] The monitoring unit continuously monitors the energy change synchronization matrix. When a line changes asynchronously with respect to other lines and shows a fixed feature, while other lines change synchronously with each other, it is considered that a ground fault occurs in the line.

[0032] A computer storage medium includes computer instructions, which, when executed on a computer, cause the computer to execute the method described above.

[0033] An electronic device, comprising:

[0034] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein:

[0035] When the processor executes the program, the method described is implemented.

[0036] Compared with the existing technology, the present invention has the following advantages: the present invention proposes the use of magnetoelectric coupling sensors to collect current signals of frequencies corresponding to the injected signals in each line, which has frequency selection characteristics and higher sensitivity to signals of the operating frequency, and uses the data collected by the magnetoelectric coupling sensors as the detection physical quantity for fault line selection; the present invention proposes a time series energy ratio to characterize the change state of the characteristic signal over time; the present invention proposes an energy change synchronization matrix as a criterion for ground fault line selection; the present invention realizes ground fault line selection in the distribution network according to its change over time by monitoring the zero-sequence current energy change synchronization matrix between each line of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are intended only to illustrate preferred embodiments and are not to be construed as limiting the present invention. It should be understood that the drawings described below are merely examples of the present invention, and that those skilled in the art will be able to derive other drawings from these drawings without inventive effort. Throughout the drawings, identical reference numerals are used to denote identical components.

[0038] In the attached figure:

[0039] Figure 1 It is a schematic flow chart of the present invention;

[0040] Figure 2 1 is a schematic diagram of a zero-sequence current waveform of the present invention;

[0041] Figure 3 It is a schematic diagram of zero-sequence current energy of the present invention;

[0042] Figure 4 This is a schematic diagram of the zero-sequence current time-sequence energy ratio of the present invention;

[0043] Figure 5 This is a schematic diagram of the energy change synchronization coefficient of the present invention (L1 line a phase fault, grounding resistance 1kΩ);

[0044] Figure 6 Schematic diagram of the energy change synchronization coefficient (L2 line a phase fault, grounding resistance 1 kΩ) of the present invention.

[0045] The present invention will be further explained below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0046] Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0047] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the invention. The scope of protection of the present invention shall be as defined in the attached claims.

[0048] To facilitate understanding of the embodiments of the present invention, further explanation will be given below using specific embodiments as examples in conjunction with the accompanying drawings, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0049] like Figures 1 to 6 As shown in FIG, the method for selecting a line for a ground fault in a distribution network includes the following steps:

[0050] Injecting a current signal of a predetermined characteristic frequency into the distribution network from the neutral point;

[0051] The current signal corresponding to the predetermined characteristic frequency in the three-phase current of each line of the distribution network is collected using the characteristic signal period as the time window length; for example, the predetermined characteristic frequency is f, and its characteristic signal period is 1 / f.

[0052] Calculating the zero-sequence current of each line of the distribution network at the predetermined characteristic frequency;

[0053] The square sum of the zero-sequence current in each time window is calculated to represent the energy of the zero-sequence current in one cycle;

[0054] The time sequence energy ratio of each line is calculated based on the ratio of the energy in adjacent time windows to characterize the change of the line zero sequence current energy over time;

[0055] Perform pairwise ratio calculations on the time series energy ratios of different lines to construct an energy change synchronization matrix;

[0056] The energy change synchronization matrix is ​​continuously monitored. When a line changes asynchronously with respect to other lines and shows a fixed feature, while other lines change synchronously with each other, it is considered that a ground fault occurs in the line.

[0057] In a preferred embodiment of the method for selecting a line for a ground fault in a distribution network, the predetermined characteristic frequency avoids power frequency harmonics of the distribution network, and the signal injection mode is a constant current source.

[0058] In a preferred embodiment of the method for selecting a ground fault line in a distribution network, a magnetoelectric coupling sensor is used to collect current signals corresponding to the predetermined characteristic frequency from the three-phase currents of each line. The operating frequency of the magnetoelectric coupling sensor is adjusted to the same characteristic frequency as the injected signal. The magnetoelectric coupling sensor has a frequency-selective characteristic and is more sensitive to signals at the operating frequency.

[0059] In a preferred embodiment of the method for selecting a ground fault line in a distribution network, the zero-sequence current of each line in the distribution network at the predetermined characteristic frequency is calculated. (1)

[0060] where i k is the zero-sequence current of the kth line, k=1,2,3,4……, i k,a 、i k,b 、i k,c are the currents of phases a, b, and c of the kth line respectively.

[0061] In a preferred embodiment of the method for selecting a ground fault line in a distribution network, the square sum of zero-sequence currents E in a time window is calculated. k [m], as shown in formula (2):

[0062] (2)

[0063] Among them, T n is the number of sampling points corresponding to one cycle length at a fixed sampling frequency, m is the time window number, t m is the starting position of the current signal corresponding to the mth time window, i k [t m +n] indicates that the kth line is at t m Zero sequence current at +n.

[0064] In a preferred embodiment of the method for selecting a ground fault line in a distribution network, the zero-sequence current time sequence energy ratio is calculated as shown in formula (3):

[0065] (3)

[0066] where r k [m] represents the zero-sequence current time sequence energy ratio at the mth time window, rk The value of [m] is always greater than 0.

[0067] In a preferred embodiment of the method for selecting a line for a ground fault in a distribution network, the energy change synchronization matrix is ​​calculated as shown in formula (4):

[0068] (4)

[0069] where a i,j [m] is the energy change synchronization coefficient of the i-th line and the j-th line in the m-th time window, a i,j The value of [m] is always greater than 0. When i=j, a i,j [m]=1, if i≠j, when a i,j [m]=1, the energy changes of the i-th line and the j-th line are completely synchronized. i,j [m]>1, the energy of the i-th line increases compared to the j-th line. The larger the value, the greater the increase. When a i,j [m]<1, the energy of the i-th line is reduced compared to the j-th line. The closer the value is to 0, the greater the reduction.

[0070] A system for implementing the method includes:

[0071] A signal injection module, used for injecting a current signal of a predetermined characteristic frequency into the neutral point;

[0072] The magnetoelectric coupling sensor array adapts to the predetermined characteristic frequency to collect the three-phase current of each line;

[0073] a calculation unit, which calculates the zero-sequence current of each line of the distribution network at the predetermined characteristic frequency, calculates the sum of the squares of the zero-sequence current in each time window to characterize the energy of the zero-sequence current in one cycle, and calculates the time-sequence energy ratio of each line based on the ratio of the energies of adjacent time windows to characterize the change of the zero-sequence current energy of the line over time;

[0074] A construction unit, which performs pairwise ratio calculations on the time series energy ratios of different lines to construct an energy change synchronization matrix;

[0075] The monitoring unit continuously monitors the energy change synchronization matrix. When a line changes asynchronously with respect to other lines and shows a fixed feature, while other lines change synchronously with each other, it is considered that a ground fault occurs in the line.

[0076] A computer storage medium includes computer instructions, which, when executed on a computer, cause the computer to execute the method described above.

[0077] An electronic device, comprising:

[0078] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein:

[0079] When the processor executes the program, the method described is implemented.

[0080] In one embodiment, the method comprises the following steps: (1) continuously injecting a current signal of a characteristic frequency from a neutral point into a distribution network; (2) collecting a current signal of a characteristic frequency corresponding to the three-phase current of each line through a magnetoelectric coupling sensor with a characteristic signal period as a time window length; (3) calculating a zero-sequence current at a characteristic frequency through the three-phase current signal; (4) calculating the square sum of the zero-sequence current in a time window to characterize the energy of the zero-sequence current in a period; (5) calculating a time-sequence energy ratio of the zero-sequence current to characterize the change of the zero-sequence current energy of the line over time; (6) taking the time-sequence energy ratio results of different lines as a matrix element to construct a zero-sequence current energy change synchronization matrix; and (7) continuously monitoring the zero-sequence current energy change synchronization matrix. When a line changes asynchronously with respect to other lines and shows a fixed feature, and when other lines change synchronously with each other, it is considered that a ground fault occurs in the line.

[0081] In one embodiment, a current signal with a characteristic frequency (configurable to 220 Hz, 833.3 Hz, and other frequencies to better match the frequency selection characteristics of the project team's in-house developed magnetoelectric sensors) is injected into the distribution network via the neutral point. The signal source operates in constant current mode. A magnetoelectric coupling sensor is connected to the line to collect the line current signal. The operating frequency of the magnetoelectric coupling sensor is adjusted to the characteristic frequency, corresponding to the frequency of the injected signal. Non-overlapping sliding window sampling is used, with the time window length equal to the period length T corresponding to the characteristic frequency.

[0082] The zero-sequence current is calculated based on the three-phase current collected by the magnetoelectric coupling sensor, as shown in formula (1):

[0083] (1)

[0084] where i k is the zero sequence current of the kth line, k=1,2,3,4... k,a 、i k,b 、i k,c are the currents of phases a, b, and c of the kth line respectively. The zero-sequence current waveform of the injected signal is as follows: Figure 2 As shown in the figure, a ground fault occurs on line 1 at 0.1s (by default, phase a is faulty and the ground resistance is 10kΩ). The envelope clearly shows that after the fault occurs, the current amplitude of line 1 first increases, then decreases and gradually stabilizes. The changes on other normal lines are the opposite.

[0085] Calculate the sum of squares of zero-sequence current E in a time window k[m], as shown in formula (2)

[0086] (2)

[0087] Among them, T n is the number of sampling points corresponding to one cycle length at a fixed sampling frequency, m is the time window number, t m is the starting position of the current signal corresponding to the mth time window, i k [t m +n] indicates that the kth line is at t m +n. Since the impedance parameters of the distribution line are difficult to obtain accurately, the present invention simplifies the process, omits the impedance effect, and directly uses the square value of the current as the approximate energy index. The zero-sequence current energy corresponding to the above zero-sequence current waveform is as follows: Figure 3 As shown in the figure, the energy of the fault line first increases, then decreases and stabilizes, which is consistent with the change trend of the zero-sequence circuit amplitude. The change of the normal line is the opposite. The energy values ​​of the normal branches are different, but the change trend is exactly the same.

[0088] The time sequence energy ratio is defined as the ratio of the energies of two adjacent time windows, which represents the relative change of the zero-sequence current energy compared to the energy of the previous time window. The zero-sequence current time sequence energy ratio is further calculated based on the calculated zero-sequence current energy, as shown in formula (3):

[0089] (3)

[0090] where r k [m] represents the zero-sequence current time sequence energy ratio at the mth time window, r k The value of [m] is always greater than 0. k [m]=1, the zero-sequence current energy does not change; when r k [m]>1, the zero-sequence current energy increases, and the larger the value, the greater the relative increase in energy; when r k [m]<1, zero sequence current energy decreases, and the closer the value is to 0, the greater the decrease. The time sequence energy ratio waveform corresponding to the above zero sequence current waveform is as follows Figure 4 As shown, the trend is consistent with the analysis results, and the time-series energy ratios of the normal lines are exactly the same. After the fault occurs, the impedance of the faulty line decreases, while the parallel equivalent value of the normal line impedance remains unchanged. The total current under the constant current source remains unchanged, and the parallel equivalent value of the impedance of the faulty and normal lines is redistributed. However, since the impedances of the normal lines remain unchanged, the shunting ratio remains constant and fixed. Therefore, the energy change of each normal line is proportional to the total energy change of the normal lines. The calculated time-series energy ratios are the same, equal to the time-series energy ratio of the total energy of the normal lines.

[0091] Construct the energy change synchronization matrix A based on the zero-sequence current time-series energy ratio of each line. The definition and calculation formula of the matrix elements are shown in formula (4).

[0092] (4)

[0093] where a i,j [m] is the energy change synchronization coefficient between the i-th line and the j-th line at the m-th time window. The value of a i,j [m] is always greater than 0. When i = j, a i,j [m] = 1. If i ≠ j, when a i,j [m] = 1, the energy changes of the i-th line and the j-th line are completely synchronized. When a i,j [m] > 1, the energy of the i-th line increases compared with the j-th line. The larger the value, the more it increases. When a i,j [m] < 1, the energy of the i-th line decreases compared with the j-th line. The closer the value is to 0, the more it decreases. Under normal conditions, the line is in a steady state, and all elements of the zero-sequence current energy change synchronization matrix are 1, as shown in Table 1. When a fault occurs, the corresponding row and column of the fault line are not 1 except for the diagonal elements, as shown in Table 2. The same conclusion holds for different grounding resistances and different line faults, as shown in Tables 3 and 4 respectively.

[0094] Table 1 Energy change synchronization matrix (normal, m = 5)

[0095]

[0096] Table 2 Energy change synchronization matrix (phase A fault of line L1, grounding resistance 10 kΩ, m = 25)

[0097]

[0098] Table 3 Energy change synchronization matrix (phase A fault of line L1, grounding resistance 1 kΩ, m = 25)

[0099]

[0100] Table 4 Energy change synchronization matrix (phase A fault of line L2, grounding resistance 1 kΩ, m = 25)

[0101]

[0102] Considering that the elements of the lower triangular matrix and the corresponding upper triangular matrix are reciprocals of each other (a j,i and a i,j are reciprocals of each other), and the diagonal elements are always 1, only the elements in the strict upper triangular matrix need to be calculated during the actual monitoring process, that is, a i,j (i < j), such as Figure 5 、 Figure 6 As shown in the figure, the results of the corresponding energy change synchronization coefficient when L1 and L2 have ground faults are shown. When the corresponding number of the fault line is in front (i.e., i corresponds to the fault line number), a i,j First increase and then decrease, conversely first decrease and then increase.

[0103] In one embodiment, the method includes,

[0104] Step 1: Signal injection and data acquisition

[0105] A constant current signal (amplitude 1A) with a frequency of f is injected from the neutral point of the distribution network;

[0106] Install magnetoelectric coupling sensors on four lines (L1 to L4) and adjust the operating frequency to f;

[0107] The signal period T = 1 / f is used as the time window length, and non-overlapping sliding window sampling is adopted (sampling frequency 10kHz, number of sampling points per window Tn=10k T).

[0108] Step 2: Zero-sequence current calculation

[0109] Based on the three-phase current collected by the magnetoelectric coupling sensor, the zero-sequence current of each line is calculated according to formula (1):

[0110] Fault setting: At t=0.1st=0.1s (corresponding to the 22nd time window), a ground fault occurs on phase a of line L1 (ground resistance 10kΩ). The zero-sequence current waveform is as follows: Figure 2 shown.

[0111] Step 3: Energy value calculation

[0112] Calculate the zero-sequence current energy in each time window according to formula (2):

[0113] The results are as follows Figure 3 As shown in the figure, the energy of the fault line L1 increases first and then decreases, while the energy change trends of the normal lines L2~L4 are consistent.

[0114] Step 4: Calculate the timing energy ratio

[0115] The energy ratio of adjacent time windows is calculated according to formula (3):

[0116] The results are as follows Figure 4 As shown in the figure: r2[m]=r3[m]=r4[m] of the normal line are always equal, while r1[m] of the fault line deviates after the fault.

[0117] Step 5: Build the Synchronicity Matrix

[0118] The energy change synchronization matrix elements are defined according to formula (4).

[0119] In one embodiment, when all non-diagonal elements in the matrix row / column corresponding to a certain line are not 1, and all matrix elements between other lines are 1, it is determined that a ground fault occurs in the line.

[0120] The characteristic frequency signal injection of the present invention solves the problem of power frequency interference. The reason why the neutral point injects a constant current signal with a frequency that is not a harmonic frequency of the power frequency of the distribution network is to avoid interference from the power frequency and harmonics such as 100Hz and 150Hz. It has been verified that injecting a constant current signal of, for example, 220Hz and 833.3Hz can also improve the signal-to-noise ratio by more than 20dB, which just overcomes the problem that the traditional power frequency method is susceptible to noise as pointed out in the background technology; in addition, the magnetoelectric coupling sensor is adapted to be tuned to the corresponding operating frequency to further suppress irrelevant frequency band signals through sensor frequency matching.

[0121] Figure 2 The zero-sequence current waveform is pure and the fault mutation characteristics are clear (the amplitude jump is obvious at 0.1s).

[0122] Time series energy ratio quantization eliminates the influence of line impedance difference, normalization processing: eliminates the absolute impedance difference of the line, fault sensitivity enhancement: ground fault causes shunt mutation, r k [m] shows amplified change trends. Table 3 shows consistent fault characteristics for 1kΩ and 10kΩ grounding resistances, demonstrating strong resistance to transient resistance. The energy change synchronization matrix is ​​the core criterion for locating faulty lines. Matrix construction reveals relative relationships: Because the shunt ratio between normal lines is fixed, fault characteristics are isolated. Sliding window energy calculation improves real-time performance and robustness. Short-term energy characterization reflects transient fault characteristics and resists fluctuation interference. The sum-of-squares operation suppresses random noise. In this invention, all matrix elements between the remaining lines are 1, and the changes are synchronized. Therefore, the matrix elements calculated for the faulty line and the remaining lines, while not 1, are equal or reciprocal (the difference between the faulty line's time-series energy ratio as the numerator or denominator depends on the matrix element subscript), demonstrating that the changes in the faulty line relative to any normal line are consistent. Furthermore, the changes in these non-1 elements over time can also be considered in fault determination. If the faulty line corresponds to the matrix element subscript i, the element will first increase from 1, then decrease to less than 1, and finally increase to around 1 and gradually stabilize. If the element is subscript j, the change is the opposite (specifically, reciprocal).

[0123] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields. The above-mentioned specific embodiments are merely illustrative and instructive, and are not restrictive. A person skilled in the art, guided by this specification and without departing from the scope of protection of the claims of the present invention, may also devise various forms, all of which fall within the scope of protection of the present invention.

Claims

1. A method for selecting a ground fault line in a distribution network, characterized in that: The steps include: Injecting a current signal of a predetermined characteristic frequency into the distribution network from the neutral point; The current signal corresponding to the predetermined characteristic frequency in the three-phase current of each line of the distribution network is collected using the characteristic signal period as the time window length; Calculating the zero-sequence current of each line of the distribution network at the predetermined characteristic frequency; The square sum of the zero-sequence current in each time window is calculated to represent the energy of the zero-sequence current in one cycle; The time sequence energy ratio of each line is calculated based on the ratio of the energy in adjacent time windows to characterize the change of the line zero sequence current energy over time; Perform pairwise ratio calculations on the time series energy ratios of different lines to construct an energy change synchronization matrix; The energy change synchronization matrix is ​​continuously monitored. When a line changes asynchronously with respect to other lines and shows a fixed feature, while other lines change synchronously with each other, it is considered that a ground fault occurs in the line.

2. A method for selecting a ground fault line in a distribution network according to claim 1, characterized in that: Preferably, the predetermined characteristic frequency avoids power frequency harmonics of the power distribution network, and the signal injection mode is a constant current source.

3. A method for selecting a ground fault line in a distribution network according to claim 1, characterized in that: The current signal corresponding to the predetermined characteristic frequency in the three-phase current of each line is collected by a magnetoelectric coupling sensor, and the operating frequency of the magnetoelectric coupling sensor is adjusted to the same characteristic frequency as the injection signal.

4. A method for selecting a ground fault line in a distribution network according to claim 1, characterized in that: Calculate the zero-sequence current of each line of the distribution network at the predetermined characteristic frequency, （1）； where i k is the zero-sequence current of the kth line, k=1,2,3,4……, i k,a 、i k,b 、i k,c are the currents of phases a, b, and c of the kth line respectively.

5. A method for selecting a ground fault line in a distribution network according to claim 1, characterized in that: Calculate the sum of squares of zero-sequence current E in a time window k [m], as shown in formula (2) （2）； Among them, T n is the number of sampling points corresponding to one cycle length at a fixed sampling frequency, m is the time window number, t m is the starting position of the current signal corresponding to the mth time window, i k [t m +n] indicates that the kth line is at t m Zero sequence current at +n.

6. A method for selecting a ground fault line in a distribution network according to claim 5, characterized in that: The zero-sequence current time sequence energy ratio is calculated as shown in formula (3): （3）； where r k [m] represents the zero-sequence current time sequence energy ratio at the mth time window, r k The value of [m] is always greater than 0.

7. A method for selecting a ground fault line in a distribution network according to claim 1, characterized in that: The calculation formula of the energy change synchronization matrix is ​​as shown in formula (4): （4）； where a i,j [m] is the energy change synchronization coefficient of the i-th line and the j-th line in the m-th time window, a i,j The value of [m] is always greater than 0. When i=j, a i,j [m]=1, if i≠j, when a i,j [m]=1, the energy changes of the i-th line and the j-th line are completely synchronized. i,j [m]>1, the energy of the i-th line increases compared to the j-th line. The larger the value, the greater the increase. When a i,j [m]<1, the energy of the i-th line is reduced compared to the j-th line. The closer the value is to 0, the greater the reduction.

8. A system for implementing the method according to any one of claims 1 to 7, characterized in that: It includes: A signal injection module, used for injecting a current signal of a predetermined characteristic frequency into the neutral point; The magnetoelectric coupling sensor array adapts to the predetermined characteristic frequency to collect the three-phase current of each line; a calculation unit, which calculates the zero-sequence current of each line of the distribution network at the predetermined characteristic frequency, calculates the sum of the squares of the zero-sequence current in each time window to characterize the energy of the zero-sequence current in one cycle, and calculates the time-sequence energy ratio of each line based on the ratio of the energies of adjacent time windows to characterize the change of the zero-sequence current energy of the line over time; A construction unit, which performs pairwise ratio calculations on the time series energy ratios of different lines to construct an energy change synchronization matrix; The monitoring unit continuously monitors the energy change synchronization matrix. When a line changes asynchronously with respect to other lines and shows a fixed feature, while other lines change synchronously with each other, it is considered that a ground fault occurs in the line.

9. A computer storage medium, characterized in that The storage medium includes computer instructions, which, when executed on a computer, enable the computer to perform the method according to any one of claims 1 to 7.

10. An electronic device, characterized in that: The electronic device comprises: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the method according to any one of claims 1 to 7 is implemented.

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