CN113702772B - High-resistance grounding fault detection method for power distribution network and related device thereof - Google Patents
High-resistance grounding fault detection method for power distribution network and related device thereof Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
Abstract
The application discloses a method for detecting a high-resistance grounding fault of a power distribution network and a related device thereof, wherein the method comprises the following steps: acquiring zero sequence current of the power distribution network; acquiring positive half cycle current and negative half cycle current of the zero sequence current, and calculating divergence of cycle current waveform based on the positive half cycle current and the negative half cycle current; comparing the divergence with a preset divergence threshold value to obtain a time domain indicating parameter; carrying out Fourier transform on the zero sequence current to obtain a plurality of even harmonic currents and odd harmonic currents; obtaining a frequency domain first indicating parameter by comparing the magnitude of the sum of the even harmonic current and the magnitude of the sum of the odd harmonic current; obtaining a frequency domain second indicating parameter by comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current; the time domain judgment parameter, the frequency domain first indication parameter and the frequency domain second indication parameter are integrated to judge whether the distribution network has the high-resistance grounding fault, and the technical problem that the detection result is not ideal in the prior art is solved.
Description
Technical Field
The application relates to the technical field of power distribution networks, in particular to a high-resistance ground fault detection method for a power distribution network and a related device thereof.
Background
Due to the fact that the types of fault medium materials, air humidity, weather environment, contact area and the like are different, the high-resistance earth fault of the power distribution network has different voltage-current characteristics. At present, the detection of the high-resistance ground fault of the power distribution network is mainly divided into time domain analysis and frequency domain analysis, wherein the time domain analysis mainly analyzes the geometric characteristics of zero-sequence voltage and zero-sequence current components, or adopts the scale profile analysis based on mathematical morphology. The frequency domain analysis adopts methods such as Fourier transform, wavelet transform, S transform and the like, harmonic components of voltage and current signals are analyzed, and third harmonic components of current and voltage are widely used for high-resistance grounding barrier tension detection.
The time domain technique is usually simple, but it assumes an infinite frequency window, which results in loss of frequency domain information, reduces the ability to extract high-impedance grounding characteristics, and makes the detection result unsatisfactory. The frequency domain technology can extract the arc characteristics of High Impedance Fault (HIF) in High frequency and low frequency, but the frequency part cannot be positioned according to time, so that the detection effectiveness is reduced. The current will change randomly due to the change of the nonlinear load; the switching of the parallel capacitors can lead the current to generate high harmonic components; power electronics components such as rectifiers or inverters can cause even harmonic components to be generated in the system, and these interference factors can reduce the accuracy of the frequency domain techniques.
Disclosure of Invention
The application provides a high-resistance grounding fault detection method for a power distribution network and a related device thereof, which are used for solving the technical problem that the detection result is not ideal in the prior art.
In view of this, the present application provides, in a first aspect, a method for detecting a high-resistance ground fault of a power distribution network, including:
acquiring zero sequence current of a power distribution network;
acquiring a positive half cycle current and a negative half cycle current of the zero sequence current, and calculating the divergence of the cycle current waveform based on the positive half cycle current and the negative half cycle current;
comparing the divergence with a preset divergence threshold value to obtain a time domain indicating parameter;
carrying out Fourier transform on the zero sequence current to obtain a plurality of even harmonic currents and odd harmonic currents;
obtaining a first frequency domain indicating parameter by comparing the sum of the even harmonic current with the sum of the odd harmonic current;
obtaining a frequency domain second indicating parameter by comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current;
and synthesizing the time domain judgment parameter, the frequency domain first indication parameter and the frequency domain second indication parameter to judge whether the power distribution network has a high-resistance grounding fault.
Optionally, the divergence calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
is the divergence of the cycle current,
is the p-th positive half-cycle current,
is the p-th negative half cycle current, and M is the maximum value of the cycle current number.
Optionally, the comparing the divergence with a preset divergence threshold value to obtain a time domain indicating parameter includes:
when the divergence is larger than or equal to a preset divergence threshold value, outputting a time domain indicating parameter with a parameter value of 1;
and when the divergence is smaller than a preset divergence threshold value, outputting a time domain indicating parameter with the parameter value of 0.
Optionally, the obtaining a frequency domain first indicator parameter by comparing the magnitude of the sum of the even harmonic current and the magnitude of the sum of the odd harmonic current includes:
calculating the sum of all even harmonic currents and the sum of all odd harmonic currents at a preset moment;
when the sum of all even harmonic currents is smaller than the sum of all odd harmonic currents, outputting a frequency domain first indicating parameter with the parameter value of 0;
counting a first duration of time for which the sum of all even harmonic currents is greater than or equal to the sum of all odd harmonic currents, starting from the preset time, when the sum of all even harmonic currents is greater than or equal to the sum of all odd harmonic currents;
and judging whether the first duration is greater than or equal to a first time threshold, if so, outputting a frequency domain first indicating parameter with a parameter value of 1, and if not, outputting a frequency domain first indicating parameter with a parameter value of 0.
Optionally, the comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current to obtain a frequency-domain second indication parameter includes:
calculating the sum of the fifth harmonic current and the seventh harmonic current at a preset moment;
when the sum of the fifth harmonic current and the seventh harmonic current is smaller than the third harmonic current, outputting a frequency domain second indicating parameter with the parameter value of 0;
counting a second duration of time for which the sum of the fifth harmonic current and the seventh harmonic current is greater than or equal to the third harmonic current from the preset time when the sum of the fifth harmonic current and the seventh harmonic current is greater than or equal to the third harmonic current;
and judging whether the second duration is greater than or equal to a second time threshold, if so, outputting a frequency domain second indicating parameter with the parameter value of 1, and if not, outputting a frequency domain second indicating parameter with the parameter value of 0.
Optionally, the step of determining whether the power distribution network has a high impedance ground fault by synthesizing the time domain determination parameter, the frequency domain first indication parameter, and the frequency domain second indication parameter includes:
calculating a product of the time domain decision parameter, the frequency domain first indicator parameter and the frequency domain second indicator parameter;
when the product is equal to a first preset parameter, judging that the distribution network has a high-resistance grounding fault;
and when the product is equal to a second preset parameter, judging that the power distribution network has no high-resistance grounding fault.
The application second aspect provides a distribution network high resistance ground fault detection device, includes:
the acquisition unit is used for acquiring the zero sequence current of the power distribution network;
the calculating unit is used for acquiring the positive half cycle current and the negative half cycle current of the zero sequence current and calculating the divergence of the cycle current waveform based on the positive half cycle current and the negative half cycle current;
the first comparison unit is used for comparing the divergence with a preset divergence threshold value to obtain a time domain indication parameter;
the transformation unit is used for carrying out Fourier transformation on the zero sequence current to obtain a plurality of even harmonic currents and odd harmonic currents;
the second comparison unit is used for comparing the sum of the even harmonic current with the sum of the odd harmonic current to obtain a frequency domain first indication parameter;
the third comparison unit is used for comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current to obtain a frequency domain second indication parameter;
and the judging unit is used for comprehensively judging whether the distribution network has the high-resistance grounding fault or not by combining the time domain judging parameter, the frequency domain first indicating parameter and the frequency domain second indicating parameter.
Optionally, the divergence calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
is the divergence of the cycle current,
is the p-th positive half-cycle current,
is the p-th negative half cycle current, and M is the maximum value of the cycle current number.
A third aspect of the application provides a high impedance ground fault detection device for a power distribution network, the device comprising a processor and a memory;
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute any one of the power distribution network high impedance ground fault detection methods according to the instructions in the program code.
A fourth aspect of the present application provides a computer-readable storage medium for storing program code, which when executed by a processor, implements the method for detecting a high impedance-to-ground fault in a power distribution network according to any one of the first aspects.
According to the technical scheme, the method has the following advantages:
the application provides a method for detecting a high-resistance grounding fault of a power distribution network, which comprises the following steps: acquiring zero sequence current of the power distribution network; acquiring positive half cycle current and negative half cycle current of the zero sequence current, and calculating divergence of cycle current waveform based on the positive half cycle current and the negative half cycle current; comparing the divergence with a preset divergence threshold value to obtain a time domain indicating parameter; carrying out Fourier transformation on the zero sequence current to obtain a plurality of even harmonic currents and odd harmonic currents; obtaining a first frequency domain indicating parameter by comparing the sum of the even harmonic current with the sum of the odd harmonic current; obtaining a frequency domain second indicating parameter by comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current; and synthesizing the time domain judgment parameter, the frequency domain first indication parameter and the frequency domain second indication parameter to judge whether the distribution network has a high-resistance grounding fault.
In the application, the distortion and the accumulation characteristic of a high-resistance grounding arc suppression waveform are considered, a time domain indicating parameter is obtained by calculating the divergence of positive and negative current waveforms, a frequency domain first indicating parameter is obtained by comparing the sum of even harmonic current and the sum of odd harmonic current, and is used for judging whether micro-signal disturbance exists, a frequency domain second indicating parameter is obtained by comparing the sum of fifth harmonic current and seventh harmonic current and the sum of third harmonic current, and is used for eliminating the interference of a nonlinear load capacitor, and finally, high-resistance grounding fault detection is carried out by combining time domain information and frequency domain information, so that the detection accuracy is improved, and the technical problem that the detection result existing in the prior art is not ideal is solved.
Drawings
In order to more clearly illustrate the embodiments of the present application 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, it is obvious that the drawings in the description below are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without inventive labor.
Fig. 1 is a schematic flowchart of a method for detecting a high-resistance ground fault of a power distribution network according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a high-resistance ground fault detection apparatus for a power distribution network according to an embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
For convenience of understanding, referring to fig. 1, an embodiment of a method for detecting a high-resistance ground fault of a power distribution network provided in the present application includes:
Zero sequence current i of power distribution network is collected t (T \82300, Δ T,2 Δ T, \8230;, T), T is current braidingThe number Δ T is the sampling interval time and T is the total number of current data points.
And 102, acquiring a positive half cycle current and a negative half cycle current of the zero sequence current, and calculating the divergence of the cycle current waveform based on the positive half cycle current and the negative half cycle current.
In the embodiment of the application, the distortion and the accumulation characteristics of the high-resistance grounding arc-suppression waveform are considered, so that time domain judgment is carried out. Acquiring cycle current of zero sequence current, wherein the cycle current comprises positive half cycle current and negative half cycle current, and the positive half cycle current is expressed as
The negative half cycle current is shown as
M is the cycle current number, M is the maximum value of the cycle current number, and t0 is the initial sampling time.
Then calculating the divergence of the cycle current waveform, wherein the calculation formula of the divergence is as follows:
in the formula (I), the compound is shown in the specification,
is the divergence of the cycle current and is,
is the p-th positive half-cycle current,
is the p-th negative half-cycle current.
And 103, comparing the divergence with a preset divergence threshold value to obtain a time domain indication parameter.
Mean divergence
Greater than or equal to the preset powderWhen the degree threshold epsilon is larger, the time domain indicating parameter with the parameter value of 1, namely index, is output t ＝1；
Mean divergence
When the time domain indicating parameter is less than the preset divergence threshold epsilon, the time domain indicating parameter with the output parameter value of 0, namely index t ＝0。
It is understood that the preset divergence threshold epsilon can be specifically valued according to actual situations, and is not specifically limited herein.
And 104, performing Fourier transform on the zero sequence current to obtain a plurality of even harmonic currents and odd harmonic currents.
Fourier transform is carried out on the zero sequence current to obtain a plurality of even harmonic currents
And odd harmonic currents
J is the harmonic order, giving a compromise between accuracy and rate, preferably J =6.
It is understood that step 102 and step 104 may be performed simultaneously or sequentially.
And 105, comparing the sum of the even harmonic current and the sum of the odd harmonic current to obtain a frequency domain first indication parameter.
Calculating the sum of all even harmonic currents and the sum of all odd harmonic currents at a preset moment;
when the sum of all even harmonic currents is smaller than the sum of all odd harmonic currents, outputting a frequency domain first indicating parameter with the parameter value being 0;
counting a first duration of time for which the sum of all even harmonic currents is greater than or equal to the sum of all odd harmonic currents, starting from the preset time, when the sum of all even harmonic currents is greater than or equal to the sum of all odd harmonic currents;
and judging whether the first duration is greater than or equal to a first time threshold, if so, outputting a frequency domain first indicating parameter with the parameter value of 1, and if not, outputting a frequency domain first indicating parameter with the parameter value of 0.
Specifically, in the embodiment of the present application, the preset time is set to k 1 Δ t, wherein k 1 =0. At a preset time k 1 Δ t, calculating the sum of all even harmonic currents
Sum of all odd harmonic currents
Judging at the preset time k 1 Δ t, sum of all even harmonic currents
Whether greater than or equal to the sum of all odd harmonic currents
When in use
The frequency domain first indicator parameter, index, with a parameter value of 0 is output p1 =0; when in use
From the preset time k 1 At start of statistics
Of the first duration. In particular, when
Updating k 1 ＝k 1 +1, i.e. cumulatively adding a sampling interval at a preset time, and then determining the updated time k 1 Sum of all even harmonic currents of Δ t
Whether greater than or equal to all odd harmonicsSum of wave currents
If yes, continuously updating k 1 ＝k 1 +1, up to
Counting to obtain the sum of all even harmonic currents
Whether greater than or equal to the sum of all odd harmonic currents
When the first duration is greater than or equal to a first time threshold T 1 Then output index p1 =1, when the first duration is less than the first time threshold T 1 Then output index p1 And =0. It will be appreciated that the first time threshold T 1 Specific values can be taken according to actual conditions, and are not specifically limited herein.
It should be noted that when
Updating k 1 ＝k 1 +1, and then judging the updated time k 1 Sum of all even harmonic currents of Δ t
Whether greater than or equal to the sum of all odd harmonic currents
If yes, then k can be determined 1 ·Δt≥T 1 If yes, directly outputting the index p1 =1, if not, continue updating k 1 ＝k 1 +1, repeat the above steps, which can save time and output the frequency domain first indication parameter more quickly.
According to the embodiment of the application, whether the sum of the even harmonic currents is greater than or equal to the sum of the odd harmonic currents and the duration are determined, so that whether weak signal disturbance exists in the power distribution network or not is determined, and the accuracy of a final detection result is improved.
And 106, comparing the sum of the fifth harmonic current and the seventh harmonic current with the third harmonic current to obtain a frequency domain second indicating parameter.
Calculating the sum of the fifth harmonic current and the seventh harmonic current at a preset moment;
when the sum of the fifth harmonic current and the seventh harmonic current is smaller than the third harmonic current, outputting a frequency domain second indicating parameter with the parameter value of 0;
counting a second duration of time for which the sum of the fifth harmonic current and the seventh harmonic current is greater than or equal to the third harmonic current from the preset time when the sum of the fifth harmonic current and the seventh harmonic current is greater than or equal to the third harmonic current;
and judging whether the second duration is greater than or equal to a second time threshold, if so, outputting a frequency domain second indicating parameter with the parameter value of 1, and if not, outputting a frequency domain second indicating parameter with the parameter value of 0.
Specifically, in the embodiment of the present application, the preset time is set to k 2 Δ t, wherein k 2 And =0. At a preset time k 2 Δ t, calculating the sum of the fifth harmonic current and the seventh harmonic current
Judging at the preset time k 2 Δ t, sum of fifth harmonic current and seventh harmonic current
Whether or not it is greater than or equal to the third harmonic current
When in use
Then output parameterFrequency domain second indicator parameter, index, of value 0 p2 =0; when in use
From the preset time k 2 At start of statistics
Of the second duration. Specifically, k is updated 2 ＝k 2 +1, i.e. cumulatively adding a sampling interval at a preset time, and then determining the updated time k 2 Sum of the fifth and seventh harmonic currents of Δ t
Whether or not it is greater than or equal to the third harmonic current
If yes, continuing to update k 2 ＝k 2 +1, up to
Is counted to obtain
When the second duration is greater than or equal to the second time threshold T 2 Then output index p2 =1, when the second duration is less than the second time threshold T 2 Then output index p2 And =0. It will be appreciated that the second time threshold T 2 Specific values can be taken according to actual conditions, and are not specifically limited herein.
It should be noted that when
Updating k 2 ＝k 2 +1, and then judging the updated time k 2 The sum of the fifth harmonic current and the seventh harmonic current of Δ t
Whether or not it is greater than or equal to the third harmonic current
If yes, then k can be determined 2 ·Δt≥T 2 If yes, directly outputting index p2 =1, if not, continue updating k 2 ＝k 2 +1, repeat the above steps, so as to save time and output the frequency domain second indication parameter more quickly.
The embodiment of the application is used for eliminating the interference of the nonlinear load capacitor by judging whether the sum of the seventh harmonic current and the fifth harmonic current is greater than or equal to the third harmonic current and the duration, so as to improve the accuracy of the final detection result.
And 107, integrating the time domain judgment parameter, the frequency domain first indication parameter and the frequency domain second indication parameter to judge whether the power distribution network has the high-resistance grounding fault.
Calculating a product of the time domain judgment parameter, the frequency domain first indication parameter and the frequency domain second indication parameter; when the product is equal to a first preset parameter, judging that the power distribution network has a high-resistance grounding fault; and when the product is equal to a second preset parameter, judging that the power distribution network has no high-resistance grounding fault.
Specifically, by calculating index t ×index p1 ×index p2 To obtain the result of high impedance grounding fault when index t ×index p1 ×index p2 If the index is not less than 1, judging that the distribution network has a high-resistance earth fault, and if the index is not less than 1 t ×index p1 ×index p2 And if the signal value is not less than 0, judging that the high-resistance grounding fault does not exist in the power distribution network.
In the embodiment of the application, the distortion and the accumulation characteristics of a high-resistance grounding arc-suppression waveform are considered, a time domain indicating parameter is obtained by calculating the divergence of positive and negative current waveforms, a frequency domain first indicating parameter is obtained by comparing the sum of even harmonic current and the sum of odd harmonic current, and is used for judging whether micro-signal disturbance exists, a frequency domain second indicating parameter is obtained by comparing the sum of fifth harmonic current and seventh harmonic current and the sum of third harmonic current, and the high-resistance grounding fault detection is carried out by combining time domain information and frequency domain information, the detection accuracy is improved, and the technical problem that the detection result in the prior art is not ideal is solved.
The above is an embodiment of a method for detecting a high-resistance ground fault of a power distribution network provided by the present application, and the following is an embodiment of a device for detecting a high-resistance ground fault of a power distribution network provided by the present application.
Referring to fig. 2, a high impedance ground fault detection apparatus for a power distribution network according to an embodiment of the present application includes:
the acquisition unit is used for acquiring the zero sequence current of the power distribution network;
the calculating unit is used for acquiring the positive half cycle current and the negative half cycle current of the zero sequence current and calculating the divergence of the waveform of the cycle current based on the positive half cycle current and the negative half cycle current;
the first comparison unit is used for comparing the divergence with a preset divergence threshold value to obtain a time domain indication parameter;
the transformation unit is used for carrying out Fourier transformation on the zero sequence current to obtain a plurality of even harmonic currents and odd harmonic currents;
the second comparison unit is used for comparing the sum of the even harmonic current with the sum of the odd harmonic current to obtain a frequency domain first indication parameter;
the third comparison unit is used for comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current to obtain a frequency domain second indication parameter;
and the judging unit is used for judging whether the power distribution network has the high-resistance grounding fault or not by integrating the time domain judging parameter, the frequency domain first indicating parameter and the frequency domain second indicating parameter.
As a further improvement, the divergence is calculated by the formula:
in the formula (I), the compound is shown in the specification,
is the divergence of the cycle current,
is the p-th positive half-cycle current,
is the p-th negative half cycle current, and M is the maximum value of the cycle current number.
As a further improvement, the first comparing unit is specifically configured to:
when the divergence is larger than or equal to a preset divergence threshold value, outputting a time domain indicating parameter with a parameter value of 1;
and when the divergence is smaller than a preset divergence threshold value, outputting a time domain indicating parameter with the parameter value of 0.
As a further improvement, the second comparing unit is specifically configured to:
calculating the sum of all even harmonic currents and the sum of all odd harmonic currents at a preset moment;
when the sum of all even harmonic currents is smaller than the sum of all odd harmonic currents, outputting a frequency domain first indicating parameter with the parameter value being 0;
counting a first duration for which the sum of all even harmonic currents is greater than or equal to the sum of all odd harmonic currents starting from the preset time when the sum of all even harmonic currents is greater than or equal to the sum of all odd harmonic currents;
and judging whether the first duration is greater than or equal to a first time threshold, if so, outputting a frequency domain first indicating parameter with the parameter value of 1, and if not, outputting a frequency domain first indicating parameter with the parameter value of 0.
As a further improvement, the third comparing unit is specifically configured to:
calculating the sum of the fifth harmonic current and the seventh harmonic current at a preset moment;
when the sum of the fifth harmonic current and the seventh harmonic current is smaller than the third harmonic current, outputting a frequency domain second indicating parameter with the parameter value of 0;
counting a second duration for which the sum of the fifth harmonic current and the seventh harmonic current is greater than or equal to the third harmonic current from the preset time when the sum of the fifth harmonic current and the seventh harmonic current is greater than or equal to the third harmonic current;
and judging whether the second duration is greater than or equal to a second time threshold, if so, outputting a frequency domain second indicating parameter with the parameter value of 1, and if not, outputting a frequency domain second indicating parameter with the parameter value of 0.
As a further improvement, the judging unit is specifically configured to:
calculating a product of the time domain judgment parameter, the frequency domain first indication parameter and the frequency domain second indication parameter;
when the product is equal to a first preset parameter, judging that the power distribution network has a high-resistance grounding fault;
and when the product is equal to a second preset parameter, judging that the power distribution network has no high-resistance grounding fault.
In the embodiment of the application, the high-resistance grounding arc suppression waveform has distortion and accumulation characteristics, a time domain indicating parameter is obtained by calculating divergence of positive and negative current waveforms, a frequency domain first indicating parameter is obtained by comparing the sum of even harmonic current and the sum of odd harmonic current, and is used for judging whether micro-signal disturbance exists, a frequency domain second indicating parameter is obtained by comparing the sum of fifth harmonic current and seventh harmonic current with the sum of third harmonic current, and is used for eliminating interference of a nonlinear load capacitor, and finally, high-resistance grounding fault detection of a power distribution network is carried out by combining time domain information and frequency domain information, so that the detection accuracy is improved, and the technical problem that the detection result existing in the prior art is not ideal is solved.
The embodiment of the application also provides a device for detecting the high-resistance grounding fault of the power distribution network, which comprises a processor and a memory;
the memory is used for storing the program codes and transmitting the program codes to the processor;
the processor is used for executing the power distribution network high resistance ground fault detection method in the foregoing method embodiment according to instructions in the program code.
The embodiment of the present application further provides a computer-readable storage medium, which is used for storing program codes, and when the program codes are executed by a processor, the method for detecting a high impedance ground fault of a power distribution network in the foregoing method embodiments is implemented.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The terms "first," "second," "third," "fourth," and the like in the description of the application and the above-described figures, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged under appropriate circumstances such that the embodiments of the application described herein may be implemented, for example, in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that in the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.
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 position, or may be distributed on multiple 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 application 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 solutions of the present application, or portions or all or portions of the technical solutions that contribute to the prior art, may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for executing all or part of the steps of the methods described in the embodiments of the present application through a computer device (which may be a personal computer, a server, or a network device). 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.
The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should 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 in the embodiments of the present application.
Claims (10)
1. A method for detecting a high-resistance ground fault of a power distribution network is characterized by comprising the following steps:
acquiring zero sequence current of a power distribution network;
acquiring positive half cycle current and negative half cycle current of the zero sequence current, and calculating divergence of cycle current waveform based on the positive half cycle current and the negative half cycle current;
comparing the divergence with a preset divergence threshold value to obtain a time domain indication parameter;
carrying out Fourier transform on the zero sequence current to obtain a plurality of even harmonic currents and odd harmonic currents;
obtaining a first frequency domain indicating parameter by comparing the sum of the even harmonic current with the sum of the odd harmonic current;
obtaining a frequency domain second indicating parameter by comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current;
and synthesizing the time domain indicating parameter, the frequency domain first indicating parameter and the frequency domain second indicating parameter to judge whether the power distribution network has a high-resistance grounding fault.
2. The method for detecting the high-resistance ground fault of the power distribution network according to claim 1, wherein the divergence calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
is the divergence of the cycle current,
for the p-th positive half-cycle current,
is the p-th negative half cycle current, and M is the maximum value of the cycle current number.
3. The method for detecting the high-resistance ground fault of the power distribution network according to claim 1, wherein the step of comparing the divergence with a preset divergence threshold value to obtain a time domain indicating parameter comprises the steps of:
when the divergence is larger than or equal to a preset divergence threshold value, outputting a time domain indicating parameter with the parameter value of 1;
and when the divergence is smaller than a preset divergence threshold value, outputting a time domain indicating parameter with the parameter value of 0.
4. The method for detecting the high-resistance ground fault of the power distribution network according to claim 1, wherein the step of obtaining the frequency domain first indicating parameter by comparing the magnitude of the sum of the even harmonic currents with the magnitude of the sum of the odd harmonic currents comprises the steps of:
calculating the sum of all even harmonic currents and the sum of all odd harmonic currents at a preset moment;
when the sum of all even harmonic currents is smaller than the sum of all odd harmonic currents, outputting a frequency domain first indicating parameter with the parameter value of 0;
counting a first duration of time for which the sum of all even harmonic currents is greater than or equal to the sum of all odd harmonic currents, starting from the preset time, when the sum of all even harmonic currents is greater than or equal to the sum of all odd harmonic currents;
and judging whether the first duration is greater than or equal to a first time threshold, if so, outputting a frequency domain first indicating parameter with a parameter value of 1, and if not, outputting a frequency domain first indicating parameter with a parameter value of 0.
5. The method for detecting the high impedance ground fault of the power distribution network according to claim 1, wherein the step of obtaining the frequency domain second indication parameter by comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current comprises:
calculating the sum of the fifth harmonic current and the seventh harmonic current at a preset moment;
when the sum of the fifth harmonic current and the seventh harmonic current is smaller than the third harmonic current, outputting a frequency domain second indicating parameter with the parameter value of 0;
counting a second duration of time for which the sum of the fifth harmonic current and the seventh harmonic current is greater than or equal to the third harmonic current from the preset time when the sum of the fifth harmonic current and the seventh harmonic current is greater than or equal to the third harmonic current;
and judging whether the second duration is greater than or equal to a second time threshold, if so, outputting a frequency domain second indicating parameter with the parameter value of 1, and if not, outputting a frequency domain second indicating parameter with the parameter value of 0.
6. The method for detecting the high-resistance ground fault of the power distribution network according to claim 1, wherein the step of determining whether the power distribution network has the high-resistance ground fault by integrating the time domain indicating parameter, the frequency domain first indicating parameter and the frequency domain second indicating parameter comprises the steps of:
calculating a product of the time domain indicating parameter, the frequency domain first indicating parameter and the frequency domain second indicating parameter;
when the product is equal to a first preset parameter, judging that the distribution network has a high-resistance grounding fault;
and when the product is equal to a second preset parameter, judging that the power distribution network has no high-resistance grounding fault.
7. The utility model provides a distribution network high resistance ground fault detection device which characterized in that includes:
the acquisition unit is used for acquiring the zero sequence current of the power distribution network;
the calculating unit is used for acquiring the positive half cycle current and the negative half cycle current of the zero sequence current and calculating the divergence of the cycle current waveform based on the positive half cycle current and the negative half cycle current;
the first comparison unit is used for comparing the divergence with a preset divergence threshold value to obtain a time domain indication parameter;
the transformation unit is used for carrying out Fourier transformation on the zero sequence current to obtain a plurality of even harmonic currents and odd harmonic currents;
the second comparison unit is used for comparing the sum of the even harmonic current with the sum of the odd harmonic current to obtain a frequency domain first indication parameter;
the third comparison unit is used for comparing the sum of the fifth harmonic current and the seventh harmonic current with the magnitude of the third harmonic current to obtain a frequency domain second indication parameter;
and the judging unit is used for comprehensively judging whether the power distribution network has the high-resistance grounding fault or not by combining the time domain indicating parameter, the frequency domain first indicating parameter and the frequency domain second indicating parameter.
8. The high impedance ground fault detection device for the power distribution network according to claim 7, wherein the divergence is calculated by the formula:
in the formula (I), the compound is shown in the specification,
is the divergence of the cycle current and is,
for the p-th positive half-cycle current,
is the p-th negative half cycle current, and M is the maximum value of the cycle current number.
9. A high-resistance ground fault detection device for a power distribution network is characterized by comprising a processor and a memory;
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the method for detecting high impedance faults in a power distribution network according to any one of claims 1 to 6 according to the instructions in the program code.
10. A computer-readable storage medium, characterized in that the computer-readable storage medium is used for storing program code, which when executed by a processor implements the method for detecting high impedance to ground faults in a power distribution network according to any one of claims 1 to 6.
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| US5475556A (en) * | 1991-04-18 | 1995-12-12 | Korea Electric Power Corporation | Apparatus for detecting high impedance fault |
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| US8170816B2 (en) * | 2008-12-29 | 2012-05-01 | General Electric Company | Parallel arc detection using discrete wavelet transforms |
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