CN113702773A - High-resistance grounding fault positioning method, device, equipment and medium for power distribution network - Google Patents
High-resistance grounding fault positioning method, device, equipment and medium for power distribution network Download PDFInfo
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- CN113702773A CN113702773A CN202111136977.2A CN202111136977A CN113702773A CN 113702773 A CN113702773 A CN 113702773A CN 202111136977 A CN202111136977 A CN 202111136977A CN 113702773 A CN113702773 A CN 113702773A
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- 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
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- 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
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- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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Abstract
The invention discloses a high-resistance earth fault positioning method, a device, equipment and a medium of a power distribution network, wherein the method comprises the following steps: acquiring a voltage sampling signal of the power distribution network according to a preset period; determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix; calculating a signal difference value between the voltage sampling signal and the voltage prediction signal, and judging whether voltage disturbance occurs according to the signal difference value; if the voltage disturbance is judged to occur, calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance; judging whether the power distribution network has a high-resistance grounding fault or not according to the energy difference percentage and the maximum signal difference; and if so, determining a high-resistance ground fault occurring line from a plurality of distribution lines in the power distribution network according to a plurality of voltage signals and a plurality of current signals before and after the occurring time, thereby accurately identifying the position of the high-resistance ground fault.
Description
Technical Field
The invention relates to the technical field of ground fault identification, in particular to a high-resistance ground fault positioning method, device, equipment and medium for a power distribution network.
Background
The distribution network is an electric power network which receives electric energy from a transmission network or a regional power plant and distributes the electric energy to various users on site through distribution facilities or step by step according to voltage. The high-resistance grounding fault is used as an indispensable electric facility in daily life, the environment of the high-resistance grounding fault is possibly complex, and if the high-resistance grounding fault is caused by the conditions that a circuit is broken and dropped, a higher object touches a high-voltage wire or a cable is subjected to insulation aging and the like, the high-resistance grounding fault is easy to occur.
The high-resistance ground fault is mainly characterized in that the resistance change range is large, the fault signal is weak, the current can randomly change due to the change of the load, when the high-resistance ground fault occurs, the transition resistance is large, the fault current randomly changes and is asymmetric, and the high-resistance ground fault has nonlinearity and obvious transient characteristics. At present, discrete wavelets and continuous wavelets are mainly adopted. And processing the transient component of the zero-sequence current by using methods such as Hilbert-Huang transform, Fourier transform and the like, and extracting characteristics such as energy, polarity, amplitude and the like to be used as fault line selection judgment.
However, the switching of the parallel capacitor can generate high harmonic component for the current, or the power electronic elements such as the rectifier or the inverter can generate even harmonic component for the system, and the weak disturbance generated by the normal operation is easy to be confused with the high-resistance ground fault, so that the position of the high-resistance ground fault cannot be accurately identified.
Disclosure of Invention
The invention provides a high-resistance grounding fault positioning method, device, equipment and medium for a power distribution network, and solves the technical problem that in the prior art, the position of a high-resistance grounding fault cannot be accurately identified due to the fact that weak disturbance generated by normal use of part of power electronic elements is easily confused with the high-resistance grounding fault.
The invention provides a high-resistance grounding fault positioning method for a power distribution network, which comprises the following steps:
acquiring a voltage sampling signal of the power distribution network according to a preset period;
determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix;
calculating a signal difference value between the voltage sampling signal and the voltage prediction signal, and judging whether voltage disturbance occurs according to the signal difference value;
if the voltage disturbance is judged to occur, calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance;
judging whether the power distribution network has a high-resistance grounding fault or not according to the energy difference percentage and the maximum signal difference;
and if so, determining a high-resistance ground fault occurrence line from a plurality of distribution lines in the distribution network according to the plurality of voltage signals and the plurality of current signals before and after the occurrence time.
Optionally, the step of determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix includes:
calculating a multiplication value between the voltage sampling signal and a preset intermediate variable matrix to obtain an intermediate sampling signal;
calculating the ratio of the sampling points of the intermediate sampling signal and the voltage sampling signal to obtain a voltage prediction signal;
the intermediate variable matrix is:
wherein, theta represents a sampling phase angle, i represents a sampling point serial number, k is a column serial number of the intermediate variable matrix, and sikThe intermediate variable is the intermediate variable of the ith row and the kth column of the intermediate variable matrix.
Optionally, the step of calculating a signal difference between the voltage sampling signal and the voltage prediction signal, and determining whether a voltage disturbance occurs according to the signal difference includes:
calculating a signal difference between the voltage sampling signal and the voltage prediction signal;
accumulating the signal difference values according to the number of the sampling points to obtain a disturbance judgment accumulated value;
comparing the disturbance judgment accumulated value with a preset disturbance threshold value;
if the disturbance judgment accumulated value is larger than the disturbance threshold value, judging that the voltage disturbance occurs in the power distribution network;
and if the disturbance judgment accumulated value is smaller than or equal to the disturbance threshold value, judging that the power distribution network is not subjected to voltage disturbance, and skipping to execute the step of acquiring the voltage sampling signal of the power distribution network according to the preset period.
Optionally, the step of calculating a percentage of energy difference and a maximum signal difference between before and after the occurrence time according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance includes:
respectively performing discrete wavelet transform on a plurality of voltage signals before and after the occurrence time of the voltage disturbance, and respectively obtaining a plurality of first voltage sampling signals before the occurrence time and a plurality of second voltage sampling signals after the occurrence time on a plurality of preset wavelet decomposition layers;
calculating an integral squared difference between the first voltage sample signal and the second voltage sample signal;
calculating a signal ratio between the integral square difference and an integral square value of the first voltage sampling signal, and determining an absolute value of the signal ratio as a percentage of energy difference before and after the occurrence time;
calculating an initial signal difference value between the first voltage sampling signal and the second voltage sampling signal;
sequentially accumulating absolute values of all the initial signal difference values to generate an intermediate signal difference corresponding to each wavelet decomposition layer;
the largest intermediate signal difference is selected from the plurality of intermediate signal differences as the largest signal difference.
Optionally, the step of determining whether the power distribution network has a high impedance ground fault according to the energy difference percentage and the maximum signal difference includes:
comparing the energy difference percentage with a preset difference threshold;
comparing the maximum signal difference with a preset signal difference threshold;
if the energy difference percentage is greater than or equal to the difference threshold value and the maximum signal difference is greater than or equal to the signal difference threshold value, determining that the power distribution network has a high-resistance ground fault;
and if the energy difference percentage is smaller than the difference threshold value or the maximum signal difference is smaller than the signal difference threshold value, judging that the high-resistance ground fault does not occur in the power distribution network.
Optionally, the step of determining a high-resistance ground fault occurrence line from among a plurality of distribution lines in the distribution network according to the voltage signal and the current signal before and after the occurrence time includes:
calculating first voltage critical values respectively corresponding to a plurality of distribution lines in the distribution network before the occurrence time according to the voltage signal and the current signal before the occurrence time;
calculating second voltage critical values respectively corresponding to a plurality of distribution lines in the distribution network after the disturbance moment according to the voltage signal and the current signal after the disturbance moment;
calculating the difference value between the second voltage critical value and the first voltage critical value, and determining the voltage critical value difference corresponding to each distribution line;
and determining the distribution line corresponding to the maximum voltage critical value difference as a high-resistance ground fault occurrence line.
The second aspect of the present invention provides a high impedance ground fault locating device for a power distribution network, including:
the voltage sampling module is used for acquiring a voltage sampling signal of the power distribution network according to a preset period;
the voltage prediction signal determination module is used for determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix;
the voltage disturbance judging module is used for calculating a signal difference value between the voltage sampling signal and the voltage predicting signal and judging whether voltage disturbance occurs according to the signal difference value;
the signal judgment quantity determining module is used for calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time of the voltage disturbance according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance if the voltage disturbance is judged to occur;
the high-resistance grounding fault judgment module is used for judging whether the power distribution network has a high-resistance grounding fault or not according to the energy difference percentage and the maximum signal difference;
and if so, determining a high-resistance ground fault occurrence line from a plurality of distribution lines in the power distribution network according to the plurality of voltage signals and the plurality of current signals before and after the occurrence time.
Optionally, the voltage prediction signal determination module includes:
the intermediate sampling signal generation submodule is used for calculating a multiplication value between the voltage sampling signal and a preset intermediate variable matrix to obtain an intermediate sampling signal;
the voltage prediction signal generation submodule is used for calculating the ratio of the sampling points of the intermediate sampling signal and the voltage sampling signal to obtain a voltage prediction signal;
the intermediate variable matrix is:
wherein, theta represents a sampling phase angle, i represents a sampling point serial number, k is a column serial number of the intermediate variable matrix, and sikThe intermediate variable is the intermediate variable of the ith row and the kth column of the intermediate variable matrix.
A third aspect of the present invention provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer program, when executed by the processor, causes the processor to perform the steps of the method for locating a high impedance earth fault of a power distribution network according to any one of the first aspect of the present invention.
A fourth aspect of the present invention provides a computer-readable storage medium, on which a computer program is stored, which, when executed, implements a method for high impedance earth fault location of a power distribution network according to any of the first aspects.
According to the technical scheme, the invention has the following advantages:
according to the method, a voltage sampling signal of the power distribution network is acquired according to a preset period; determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix; calculating a signal difference value between the voltage sampling signal and the voltage prediction signal, and judging whether voltage disturbance occurs according to the signal difference value; if the voltage disturbance is judged to occur, calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance; judging whether the power distribution network has a high-resistance grounding fault or not according to the energy difference percentage and the maximum signal difference; and if so, determining a high-resistance ground fault occurrence line from a plurality of distribution lines in the distribution network according to a plurality of voltage signals and a plurality of current signals before and after the occurrence time. Therefore, the technical problem that the position of the high-resistance ground fault cannot be accurately identified due to the fact that weak disturbance generated by normal use of part of power electronic elements is easily confused with the high-resistance ground fault in the prior art is solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
Fig. 1 is a flowchart illustrating steps of a method for locating a high impedance ground fault of a power distribution network according to an embodiment of the present invention;
FIG. 2 is a flow chart of the steps for calculating the percentage of energy difference and the maximum signal difference in an embodiment of the present invention;
fig. 3 is a block diagram of a high-resistance ground fault locating device for a power distribution network according to an embodiment of the present invention.
Detailed Description
The embodiment of the invention provides a high-resistance ground fault positioning method, a high-resistance ground fault positioning device, equipment and a medium for a power distribution network, which are used for solving the technical problem that in the prior art, the position of a high-resistance ground fault cannot be accurately identified due to the fact that weak disturbance generated by normal use of part of power electronic elements is easily confused with the high-resistance ground fault.
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a flowchart illustrating a method for locating a high-impedance ground fault of a power distribution network according to an embodiment of the present invention.
The invention provides a high-resistance grounding fault positioning method of a power distribution network, which comprises the following steps:
the voltage sampling signal refers to a signal for sampling voltage at a preset sampling rate, and is generally expressed in a cycle form, which may be specifically expressed as:
wherein i represents the serial number of a sampling point, and n represents the number of sampling points in a cycle; u shapemWhich is indicative of the magnitude of the voltage,
denotes the phase angle, theta denotes the sampling phase angle.
In the embodiment of the application, in order to obtain a data basis for determining whether the power distribution network has a high-resistance ground fault, the bus voltage of the power distribution network can be collected according to a preset period to serve as a voltage sampling signal.
It should be noted that the preset period may be configured according to a sampling rate, and besides the bus voltage, data such as current and phase angle of the power distribution network bus may be acquired at the same time.
after the voltage sampling signal is obtained, in order to judge whether weak voltage disturbance occurs to the power distribution network at the current moment, conversion can be performed based on the voltage sampling signal and a preset intermediate variable matrix, so that voltage estimation is performed according to the collected voltage sampling signal, and a voltage prediction signal is determined.
Optionally, step 102 may comprise the sub-steps of:
calculating a multiplication value between the voltage sampling signal and a preset intermediate variable matrix to obtain an intermediate sampling signal;
calculating the ratio of the sampling points of the intermediate sampling signal and the voltage sampling signal to obtain a voltage prediction signal;
the intermediate variable matrix is:
wherein, theta represents a sampling phase angle, i represents a sampling point serial number, k is a column serial number of the intermediate variable matrix, and sikIs the intermediate variable of the ith row and the kth column of the intermediate variable matrix.
In a specific implementation, the voltage sampling signal u is acquirediThen, it can be expressed in the form of a vector as:
where j is the imaginary component.
According to the voltage sampling signal uiThe voltage prediction signal obtained by the vector calculation is;
wherein YR and YI represent the real and imaginary parts of the voltage sample signal;
performing discrete Fourier transform on the vector to obtain:
combining the above formulas, the following formula is obtained:
wherein S ═ { S ═ Sik}。
In the embodiment of the application, the intermediate sampling signal is obtained by calculating the multiplication value between the voltage sampling signal and the preset intermediate variable matrix, and then the ratio of the number of sampling points of the intermediate sampling signal and the voltage sampling signal is calculated to obtain the voltage prediction signal.
further, step 103 may comprise the following sub-steps:
calculating a signal difference between the voltage sampling signal and the voltage prediction signal;
accumulating the signal difference values according to the number of sampling points to obtain a disturbance judgment accumulated value;
comparing the disturbance judgment accumulated value with a preset disturbance threshold value;
if the disturbance judgment accumulated value is larger than the disturbance threshold value, judging that the voltage disturbance occurs in the power distribution network;
and if the disturbance judgment accumulated value is smaller than or equal to the disturbance threshold value, judging that the power distribution network does not generate voltage disturbance, and skipping to execute the step of acquiring the voltage sampling signal of the power distribution network according to a preset period.
In the embodiment of the application, in order to provide a data determination basis for subsequent voltage disturbance, the deviation between the voltage sampling signal and the voltage prediction signal needs to be calculated, and at this time, the deviation can be calculatedSignal difference between voltage sampling signal and voltage prediction signal
In the calculation, the signal difference value is obtained
Then, in order to obtain a weak disturbance judgment factor, that is, a disturbance judgment accumulated value sdi, the signal difference value may be further accumulated according to the number of sampling points to obtain the disturbance judgment accumulated value sdi:
after the disturbance judgment accumulated value sdi is obtained, the disturbance judgment accumulated value sdi can be compared with a preset disturbance threshold value, if the sdi is larger than the disturbance threshold value, the fact that voltage disturbance occurs to the power distribution network at the moment is indicated, high-resistance grounding faults may exist, and further identification can be continued at the moment; if the sdi is smaller than or equal to the disturbance threshold, the voltage disturbance of the power distribution network does not occur at the moment, and the voltage sampling signal of the power distribution network can be continuously acquired according to the preset period at the moment, so that the continuous monitoring of the power distribution network is realized.
104, if the voltage disturbance is judged to occur, calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance;
optionally, step 104 may include the following sub-steps S11-S15:
s11, respectively carrying out discrete wavelet transform on a plurality of voltage signals before and after the occurrence time of voltage disturbance, and respectively obtaining a plurality of first voltage sampling signals before the occurrence time and a plurality of second voltage sampling signals after the occurrence time on a plurality of preset wavelet decomposition layers;
discrete wavelet transform refers to discretizing the scale and translation of the basic wavelet. In general, a binary discrete process is used in computer implementation, and the wavelet subjected to the discretization and the corresponding wavelet transform are converted into discrete wavelet transform (DWT for short). In practice, the discrete wavelet transform is obtained by discretizing the scale and displacement of the continuous wavelet transform by a power of 2, and is also called binary wavelet transform.
In this embodiment of the present application, after obtaining a plurality of voltage signals before and after the occurrence time of voltage disturbance, discrete wavelet transform may be performed on each voltage signal, and a plurality of first voltage sampling signals before the occurrence time and a plurality of second voltage sampling signals after the occurrence time are obtained in a plurality of preset wavelet decomposition layers, respectively.
Specifically, m voltage and current cycle data before occurrence time can be collected, namely, a voltage signal upre，
And m cycle voltage data after the occurrence time, i.e. voltage signal upost，
Wherein a represents the cycle number of the voltage signal. Then to
Analyzing by adopting discrete wavelet transform, and acquiring a first voltage sampling signal after wavelet analysis by adopting a Debyce 4 th mother wavelet decomposition signal to a plurality of preset wavelet decomposition layers, such as a q-th layer, wherein q is generally 5-8
And a second voltage sampling signal
S12, calculating the integral square difference between the first voltage sampling signal and the second voltage sampling signal;
s13, calculating a signal ratio between the integral square difference and the integral square value of the first voltage sampling signal, and determining the absolute value of the signal ratio as the energy difference percentage before and after the occurrence moment;
after the first voltage sampling signal and the second voltage sampling signal are obtained, in order to calculate the energy difference percentage before and after the voltage disturbance occurs, the integral square difference between the first voltage sampling signal and the second voltage sampling signal and the integral square value of the first voltage sampling signal can be further calculated, and the absolute value of the signal ratio between the integral square difference and the integral square value is determined as the energy difference percentage before and after the voltage disturbance occurs.
In a specific implementation, the above process may be implemented by writing a formula:
wherein ep is the percentage of energy difference,
in order to sample the signal for the first voltage,
the second voltage sampling signal.
S14, calculating an initial signal difference value between the first voltage sampling signal and the second voltage sampling signal;
s15, sequentially accumulating absolute values of all initial signal difference values to generate intermediate signal differences corresponding to each wavelet decomposition layer;
and S16, selecting the largest intermediate signal difference from the plurality of intermediate signal differences as the largest signal difference.
The maximum signal difference before and after the occurrence moment of the voltage disturbance can be calculated while the energy difference percentage is calculated, firstly, the initial signal difference value in each wavelet decomposition layer can be calculated, then, the absolute values of all the initial signal difference values are further accumulated, and the intermediate signal difference delta d [ q ] corresponding to each wavelet decomposition layer is generated:
then, the maximum intermediate signal difference is selected from the plurality of intermediate signal differences as the maximum signal difference Δ d:
Δd＝max(Δd[q])，q＝1,2...Q
further, step 105 may comprise the following sub-steps:
comparing the energy difference percentage with a preset difference threshold;
comparing the maximum signal difference with a preset signal difference threshold;
if the energy difference percentage is greater than or equal to the difference threshold value and the maximum signal difference is greater than or equal to the signal difference threshold value, determining that the high-resistance ground fault occurs in the power distribution network;
and if the energy difference percentage is smaller than the difference threshold value or the maximum signal difference is smaller than the signal difference threshold value, judging that the high-resistance grounding fault does not occur in the power distribution network.
In one example of the present application, after calculating the energy difference percentage and the maximum signal difference, the energy difference percentage and the difference threshold may be further compared, and the maximum signal difference and the signal difference threshold; if the energy difference percentage is greater than or equal to the difference threshold value and the maximum signal difference is greater than or equal to the signal difference threshold value, determining that the high-resistance ground fault occurs in the power distribution network; and if the energy difference percentage is smaller than the difference threshold value or the maximum signal difference is smaller than the signal difference threshold value, judging that the high-resistance grounding fault does not occur in the power distribution network.
It should be noted that the difference threshold may be set to 2, and the signal difference threshold may be set to 3, and the specific value of the threshold is not limited in the embodiment of the present application.
And 106, if so, determining a high-resistance ground fault occurrence line from a plurality of distribution lines in the power distribution network according to the plurality of voltage signals and the plurality of current signals before and after the occurrence time.
In another example of the present application, step 106 may include the following sub-steps:
calculating first voltage critical values respectively corresponding to a plurality of distribution lines in the power distribution network before the occurrence time according to the voltage signal and the current signal before the occurrence time;
calculating second voltage critical values respectively corresponding to a plurality of distribution lines in the power distribution network after the disturbance moment according to the voltage signal and the current signal after the disturbance moment;
calculating the difference value between the second voltage threshold and the first voltage threshold, and determining the voltage threshold difference corresponding to each distribution line;
and determining the distribution line corresponding to the maximum voltage critical value difference as a high-resistance ground fault occurrence line.
In the embodiment of the application, if it is determined that the power distribution network has the high-resistance ground fault, the current signal i before and after the occurrence time can be further acquiredpreAnd ipostIn combination with the aforementioned voltage signal upreAnd upostAnd further calculating a first voltage critical value of each distribution line of the power distribution network before the occurrence moment and a second voltage critical value of each distribution line of the power distribution network after the occurrence moment, determining voltage critical value differences corresponding to the distribution lines respectively by calculating a difference value between the second voltage critical value and the first voltage critical value, and determining the distribution line corresponding to the maximum voltage critical value difference as a high-resistance ground fault occurrence line.
In a specific implementation, the calculation may be performed in the following manner:
1. calculating the voltage signal change difference delta u before and after the occurrence time0Difference Δ i of sum current signal variation0：
2. According to the impedance of each distribution line and the combined voltage signal variation difference delta u0Difference Δ i of sum current signal variation0And calculating a first voltage critical value of the distribution line X:
3. calculating a second voltage critical value of the distribution line X:
4. calculating the voltage critical value difference | delta u of the distribution line X based on the second voltage critical value and the first voltage critical valuee-Δuc|。
Wherein c, d, e and f are distribution line numbers respectively. Δ ucRepresenting a line X voltage value inferred from pre-fault impedance and voltage variation; Δ ueRepresenting the line X voltage value inferred from post-fault impedance and voltage variation; Δ uc-1Indicating an inferred voltage value, Delauu, of an adjacent line (line number less than c)e+1Represents the estimated voltage of the adjacent line (line number is larger than e); Δ idRepresents the current variation of the line d; Δ ifRepresents the amount of change in current, z, of line fc-1Represents the impedance of the line c-1, zeRepresenting the impedance of line e.
In the embodiment of the application, a voltage sampling signal of the power distribution network is acquired according to a preset period; determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix; calculating a signal difference value between the voltage sampling signal and the voltage prediction signal, and judging whether voltage disturbance occurs according to the signal difference value; if the voltage disturbance is judged to occur, calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance; judging whether the power distribution network has a high-resistance grounding fault or not according to the energy difference percentage and the maximum signal difference; and if so, determining a high-resistance ground fault occurrence line from a plurality of distribution lines in the distribution network according to a plurality of voltage signals and a plurality of current signals before and after the occurrence time. Therefore, the technical problem that the position of the high-resistance ground fault cannot be accurately identified due to the fact that weak disturbance generated by normal use of part of power electronic elements is easily confused with the high-resistance ground fault in the prior art is solved.
Referring to fig. 3, fig. 3 is a block diagram of a high impedance ground fault locating device of a power distribution network according to an embodiment of the present invention.
The embodiment of the invention provides a high-resistance grounding fault positioning device of a power distribution network, which comprises:
the voltage sampling module 301 is configured to obtain a voltage sampling signal of the power distribution network according to a preset period;
a voltage prediction signal determination module 302, configured to determine a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix;
the voltage disturbance judgment module 303 is configured to calculate a signal difference between the voltage sampling signal and the voltage prediction signal, and judge whether voltage disturbance occurs according to the signal difference;
a signal determination amount determining module 304, configured to calculate, if it is determined that voltage disturbance occurs, an energy difference percentage and a maximum signal difference before and after an occurrence time according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance;
the high-resistance ground fault judgment module 305 is configured to judge whether a high-resistance ground fault occurs in the power distribution network according to the energy difference percentage and the maximum signal difference;
and a fault occurrence line positioning module 306, configured to determine, if yes, a high-resistance ground fault occurrence line from multiple distribution lines in the power distribution network according to multiple voltage signals and multiple current signals before and after the occurrence time.
Optionally, the voltage prediction signal determination module 302 includes:
the intermediate sampling signal generation submodule is used for calculating a multiplication value between the voltage sampling signal and a preset intermediate variable matrix to obtain an intermediate sampling signal;
the voltage prediction signal generation submodule is used for calculating the ratio of the sampling points of the intermediate sampling signal and the voltage sampling signal to obtain a voltage prediction signal;
the intermediate variable matrix is:
wherein, theta represents a sampling phase angle, i represents a sampling point serial number, k is a column serial number of the intermediate variable matrix, and sikIs the intermediate variable of the ith row and the kth column of the intermediate variable matrix.
Optionally, the voltage disturbance determining module 303 includes:
the signal difference value calculation submodule is used for calculating a signal difference value between the voltage sampling signal and the voltage prediction signal;
the disturbance accumulation submodule is used for accumulating the signal difference value according to the number of the sampling points to obtain a disturbance judgment accumulated value;
the disturbance comparison submodule is used for comparing the disturbance judgment accumulated value with a preset disturbance threshold value;
the first disturbance judgment submodule is used for judging that the voltage disturbance occurs in the power distribution network if the disturbance judgment accumulated value is larger than the disturbance threshold value;
and the second disturbance judgment submodule is used for judging that the power distribution network is not subjected to voltage disturbance if the disturbance judgment accumulated value is smaller than or equal to the disturbance threshold value, and skipping to execute the step of acquiring the voltage sampling signal of the power distribution network according to the preset period.
Alternatively, the signal judgment amount determination module 304 includes:
the signal transformation submodule is used for respectively carrying out discrete wavelet transformation on a plurality of voltage signals before and after the occurrence time of voltage disturbance, and respectively obtaining a plurality of first voltage sampling signals before the occurrence time and a plurality of second voltage sampling signals after the occurrence time on a plurality of preset wavelet decomposition layers;
the integral square error calculation submodule is used for calculating the integral square error between the first voltage sampling signal and the second voltage sampling signal;
the energy difference percentage calculation submodule is used for calculating a signal ratio between the integral square difference and an integral square value of the first voltage sampling signal and determining an absolute value of the signal ratio as the energy difference percentage before and after the occurrence moment;
the initial signal difference value calculation submodule is used for calculating an initial signal difference value between the first voltage sampling signal and the second voltage sampling signal;
the intermediate signal difference calculation submodule is used for accumulating absolute values of all the initial signal difference values in sequence to generate an intermediate signal difference corresponding to each wavelet decomposition layer;
and the maximum signal difference selection submodule is used for selecting the maximum intermediate signal difference from the plurality of intermediate signal differences as the maximum signal difference.
Optionally, the high-resistance ground fault determining module 305 includes:
the difference comparison submodule is used for comparing the energy difference percentage with a preset difference threshold;
the signal difference comparison submodule is used for comparing the maximum signal difference with a preset signal difference threshold;
the first ground fault judgment submodule is used for judging that the power distribution network has a high-resistance ground fault if the energy difference percentage is greater than or equal to a difference threshold and the maximum signal difference is greater than or equal to a signal difference threshold;
and the second ground fault judgment submodule is used for judging that the high-resistance ground fault does not occur in the power distribution network if the energy difference percentage is smaller than the difference threshold or the maximum signal difference is smaller than the signal difference threshold.
Optionally, the fault occurrence line locating module 306 includes:
the first voltage threshold operator module is used for calculating first voltage thresholds respectively corresponding to a plurality of distribution lines in the power distribution network before the occurrence time according to the voltage signal and the current signal before the occurrence time;
the second voltage threshold operator module is used for calculating second voltage thresholds respectively corresponding to a plurality of distribution lines in the power distribution network after the disturbance moment according to the voltage signal and the current signal after the disturbance moment;
the voltage critical value difference calculation submodule is used for calculating the difference value between the second voltage critical value and the first voltage critical value and determining the voltage critical value difference corresponding to each distribution line;
and the high-resistance ground fault occurring line determining submodule is used for determining the distribution line corresponding to the maximum voltage critical value difference as the high-resistance ground fault occurring line.
The embodiment of the present invention further provides an electronic device, which includes a memory and a processor, where the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for locating a high impedance ground fault of a power distribution network according to any embodiment of the present invention.
Embodiments of the present invention further provide a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed, implements a method for locating a high impedance ground fault of a power distribution network according to any embodiment of the present invention.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described apparatuses, modules and sub-modules may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
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 units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. 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.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A high-resistance grounding fault positioning method of a power distribution network is characterized by comprising the following steps:
acquiring a voltage sampling signal of the power distribution network according to a preset period;
determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix;
calculating a signal difference value between the voltage sampling signal and the voltage prediction signal, and judging whether voltage disturbance occurs according to the signal difference value;
if the voltage disturbance is judged to occur, calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance;
judging whether the power distribution network has a high-resistance grounding fault or not according to the energy difference percentage and the maximum signal difference;
and if so, determining a high-resistance ground fault occurrence line from a plurality of distribution lines in the distribution network according to the plurality of voltage signals and the plurality of current signals before and after the occurrence time.
2. The method of claim 1, wherein the step of determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix comprises:
calculating a multiplication value between the voltage sampling signal and a preset intermediate variable matrix to obtain an intermediate sampling signal;
calculating the ratio of the sampling points of the intermediate sampling signal and the voltage sampling signal to obtain a voltage prediction signal;
the intermediate variable matrix is:
wherein, theta represents a sampling phase angle, i represents a sampling point serial number, k is a column serial number of the intermediate variable matrix, and sikThe intermediate variable is the intermediate variable of the ith row and the kth column of the intermediate variable matrix.
3. The method of claim 2, wherein the step of calculating a signal difference between the voltage sampling signal and the voltage prediction signal and determining whether a voltage disturbance occurs based on the signal difference comprises:
calculating a signal difference between the voltage sampling signal and the voltage prediction signal;
accumulating the signal difference values according to the number of the sampling points to obtain a disturbance judgment accumulated value;
comparing the disturbance judgment accumulated value with a preset disturbance threshold value;
if the disturbance judgment accumulated value is larger than the disturbance threshold value, judging that the voltage disturbance occurs in the power distribution network;
and if the disturbance judgment accumulated value is smaller than or equal to the disturbance threshold value, judging that the power distribution network is not subjected to voltage disturbance, and skipping to execute the step of acquiring the voltage sampling signal of the power distribution network according to the preset period.
4. The method of claim 1, wherein the step of calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time of the voltage disturbance from a plurality of voltage signals before and after the occurrence time comprises:
respectively performing discrete wavelet transform on a plurality of voltage signals before and after the occurrence time of the voltage disturbance, and respectively obtaining a plurality of first voltage sampling signals before the occurrence time and a plurality of second voltage sampling signals after the occurrence time on a plurality of preset wavelet decomposition layers;
calculating an integral squared difference between the first voltage sample signal and the second voltage sample signal;
calculating a signal ratio between the integral square difference and an integral square value of the first voltage sampling signal, and determining an absolute value of the signal ratio as a percentage of energy difference before and after the occurrence time;
calculating an initial signal difference value between the first voltage sampling signal and the second voltage sampling signal;
sequentially accumulating absolute values of all the initial signal difference values to generate an intermediate signal difference corresponding to each wavelet decomposition layer;
the largest intermediate signal difference is selected from the plurality of intermediate signal differences as the largest signal difference.
5. The method of claim 1, wherein said step of determining whether a high impedance ground fault has occurred in said power distribution network based on said percentage of energy difference and said maximum signal difference comprises:
comparing the energy difference percentage with a preset difference threshold;
comparing the maximum signal difference with a preset signal difference threshold;
if the energy difference percentage is greater than or equal to the difference threshold value and the maximum signal difference is greater than or equal to the signal difference threshold value, determining that the power distribution network has a high-resistance ground fault;
and if the energy difference percentage is smaller than the difference threshold value or the maximum signal difference is smaller than the signal difference threshold value, judging that the high-resistance ground fault does not occur in the power distribution network.
6. The method of claim 1, wherein said step of determining a high impedance ground fault occurring line from a plurality of distribution lines within said distribution network based on said voltage signal and current signal before and after said time of occurrence comprises:
calculating first voltage critical values respectively corresponding to a plurality of distribution lines in the distribution network before the occurrence time according to the voltage signal and the current signal before the occurrence time;
calculating second voltage critical values respectively corresponding to a plurality of distribution lines in the distribution network after the disturbance moment according to the voltage signal and the current signal after the disturbance moment;
calculating the difference value between the second voltage critical value and the first voltage critical value, and determining the voltage critical value difference corresponding to each distribution line;
and determining the distribution line corresponding to the maximum voltage critical value difference as a high-resistance ground fault occurrence line.
7. A high resistance ground fault locating device of a power distribution network is characterized by comprising:
the voltage sampling module is used for acquiring a voltage sampling signal of the power distribution network according to a preset period;
the voltage prediction signal determination module is used for determining a voltage prediction signal based on the voltage sampling signal and a preset intermediate variable matrix;
the voltage disturbance judging module is used for calculating a signal difference value between the voltage sampling signal and the voltage predicting signal and judging whether voltage disturbance occurs according to the signal difference value;
the signal judgment quantity determining module is used for calculating the percentage of energy difference and the maximum signal difference before and after the occurrence time of the voltage disturbance according to a plurality of voltage signals before and after the occurrence time of the voltage disturbance if the voltage disturbance is judged to occur;
the high-resistance grounding fault judgment module is used for judging whether the power distribution network has a high-resistance grounding fault or not according to the energy difference percentage and the maximum signal difference;
and if so, determining a high-resistance ground fault occurrence line from a plurality of distribution lines in the power distribution network according to the plurality of voltage signals and the plurality of current signals before and after the occurrence time.
8. The apparatus of claim 7, wherein the voltage prediction signal determination module comprises:
the intermediate sampling signal generation submodule is used for calculating a multiplication value between the voltage sampling signal and a preset intermediate variable matrix to obtain an intermediate sampling signal;
the voltage prediction signal generation submodule is used for calculating the ratio of the sampling points of the intermediate sampling signal and the voltage sampling signal to obtain a voltage prediction signal;
the intermediate variable matrix is:
wherein, theta represents a sampling phase angle, i represents a sampling point serial number, k is a column serial number of the intermediate variable matrix, and sikThe intermediate variable is the intermediate variable of the ith row and the kth column of the intermediate variable matrix.
9. An electronic device, characterized in that it comprises a memory and a processor, the memory having stored therein a computer program, which, when executed by the processor, causes the processor to carry out the steps of the method for high impedance earth fault location of an electrical distribution network according to any of claims 1-6.
10. A computer-readable storage medium, on which a computer program is stored, which, when executed, implements a method for high impedance earth fault location of a power distribution network according to any of claims 1-6.
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