CN117148212A - Single-phase earth fault line selection method for small-current grounding system of micro-grid power distribution network - Google Patents
Single-phase earth fault line selection method for small-current grounding system of micro-grid power distribution network Download PDFInfo
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Abstract
The application discloses a single-phase earth fault line selection method of a small-current grounding system of a micro-grid power distribution network, which comprises the following steps: constructing a small-current grounding power distribution network system containing a micro-grid; simulating occurrence of single-phase earth fault on system line; collecting the voltage and current of each circuit when the system operates; calculating zero sequence components of all the lines of the system according to the collected voltages and currents of all the lines; extracting fifth harmonic components of zero sequence components of all lines in the system; and respectively comparing and selecting the amplitude, the phase and the polarity of the fifth harmonic component, and integrating the amplitude, the phase and the polarity to select the fault line. According to the application, the higher harmonic characteristics of each circuit are extracted when the system operates, the amplitude, the phase and the polarity of the characteristic components of the five-harmonic fault are comprehensively compared by using a five-harmonic method, and the line selection result is compared, so that the single-phase grounding fault line selection of the micro-grid power distribution network is accurately and rapidly realized, and the technical support is provided for the safe and reliable operation of the micro-grid power distribution network system.
Description
Technical Field
The application belongs to the technical field of power grid fault detection of a power distribution network, and particularly relates to a single-phase grounding fault line selection method of a small-current grounding system of a micro-grid power distribution network.
Background
In the current low-voltage distribution network, three grounding modes exist for the neutral point, namely, the neutral point is not grounded, the neutral point is grounded through an arc suppression coil, and the neutral point is grounded through high resistance, and the neutral point is commonly called as a small-current grounding system. According to the statistics of the power operation faults, single-phase ground faults are most common in a small-current ground distribution network system, and the occurrence rate is highest and exceeds 80% of the total faults. In addition, when the small-current grounding system has single-phase grounding faults, the system can continue to operate for 1-2 hours under the fault condition due to the small fault voltage and fault current. Therefore, in order to prevent the long-term overvoltage from causing insulation breakdown of other phases, single-phase earth faults develop into interphase faults, power supply is affected, and it is very important to rapidly and accurately select a fault line under the conditions of not interrupting power supply continuity and guaranteeing safety.
At present, a single-phase earth fault line selection method of a small-current grounding system applied in a power system is mainly divided into a line selection method based on a steady-state component, a line selection method based on a transient component and an external injection method. The line selection method based on the transient component is sensitive, but the transient process of the single-phase earth fault of the power distribution network is short, and the transient process of the single-phase earth fault is difficult to be accurately mastered; the external injection method has low universality and practicality due to the need of additional equipment; the line selection method based on the steady-state component is based on the fault signal of the single-phase grounding fault, and most of the line selection methods are directed against the zero-sequence component of the system, including a group ratio phase method, a power frequency reactive direction method, a negative sequence current method, a fifth harmonic method and the like, and have certain stability and accuracy, but in some systems, the steady-state fault characteristics of a small-current grounding system are weaker, and the sensitivity of line selection can be influenced.
Distributed power generation is a new power generation mode, and is mainly based on the utilization of dispersed energy. Unlike centralized power generation, distributed power generation is typically distributed into medium-low voltage distribution networks according to local conditions, becoming a micro-grid. In a power distribution network with a micro-grid, the original unidirectional power flow is converted into bidirectional power flow and even reverse power flow, so that the operation control of the power distribution network is more complex, and a series of electric energy quality problems are brought. Unlike a single power distribution network, there is a bidirectional power flow in the distribution network with a micro-grid, so that the power frequency physical quantity of each line in the system is different, which affects the original fault characteristics to a certain extent and makes the system more complex. The existing single-phase earth fault line selection technology of the power distribution network is not suitable for fault line selection after single-phase earth faults of the micro-grid power distribution network, so that research on the single-phase earth fault line selection technology of the micro-grid power distribution network is needed.
Disclosure of Invention
In order to solve the problem that the existing single-phase earth fault line selection technology of the power distribution network is not suitable for fault line selection after the single-phase earth fault of the micro-grid power distribution network, the application provides a single-phase earth fault line selection method of a small-current grounding system of the micro-grid power distribution network.
The application is realized by the following technical scheme:
a method for selecting a single-phase earth fault of a small-current grounding system of a micro-grid power distribution network, the method comprising:
constructing a small-current grounding power distribution network system containing a micro-grid;
simulating occurrence of single-phase earth faults on the small-current grounded power distribution network system line;
collecting the voltage and current of each circuit when the small-current grounding power distribution network system operates;
calculating zero sequence components of all the lines of the small-current grounding power distribution network system according to the collected voltages and currents of all the lines;
extracting fifth harmonic components of zero sequence components of all lines in the small-current grounding power distribution network system;
and respectively comparing and selecting the amplitude, the phase and the polarity of the fifth harmonic component, and integrating amplitude, phase and polarity comparison and selecting results to perform fault line selection.
The existing power system mainly adopts a single-phase grounding fault line selection method based on a steady-state component or a transient component, however, the transient process of the grounding fault of the power distribution network is difficult to accurately grasp due to the short transient process of the grounding fault of the power distribution network, so that the grounding fault line selection cannot be rapidly and accurately realized; the line selection method based on the steady-state component depends on the signal of the fault, and the micro-grid distribution has the condition of bidirectional power flow, and the fault characteristics are complex, so that the existing single line selection scheme based on the transient component and the steady-state component can not realize the single-phase earth fault line selection of the micro-grid distribution. The application provides a single-phase grounding fault line selection technology special for a micro-grid power distribution network, which is characterized in that the high-order harmonic characteristics of each line are extracted when a system operates, the five-order harmonic in the zero-sequence characteristic high-order harmonic is selected by a five-order harmonic method to perform fault characteristic comparison line selection, and finally the amplitude, phase and polarity comparison line selection results of the five-order harmonic components are synthesized, so that the single-phase grounding fault line selection of the micro-grid power distribution network is rapidly and accurately realized.
As an optimal implementation mode, the application builds a small-current grounding power distribution network system containing a micro-grid, which comprises the following specific steps:
three lines are respectively led out from a power supply, the voltage levels of the three lines are the same and are 10kV, and the three lines are connected with different loads;
and connecting another power source with the same voltage level, namely a micro-grid, to the position of the first line close to the load side transformer.
As a preferred embodiment, the method for calculating the zero sequence component of each line specifically comprises the following steps:
constructing a zero sequence voltage calculation module and a zero sequence current calculation module by the adder and the multiplier;
wherein the zero sequence current is equal to the sum of the phasors of the three phases multiplied by one third, and the zero sequence voltage is equal to the sum of the phasors of the three phases multiplied by one third.
As a preferred embodiment, the application adopts FFT algorithm to extract the fifth harmonic component of the zero sequence component of each line.
As a preferred embodiment, the amplitude, phase and polarity comparison line selection of the fifth harmonic component is performed respectively, specifically:
comparing the amplitude, phase or polarity of the fifth harmonic components of all lines in the system in pairs;
and then performing logic AND operation on all relevant comparison results of the same circuit, and if the logic AND result is high level, indicating that the amplitude, the phase or the polarity of the circuit is abnormal.
As a preferred implementation mode, the comprehensive amplitude, phase and polarity comparison line selection result of the application is used for fault line selection, and specifically comprises the following steps:
and performing logic AND operation on the amplitude, phase and polarity comparison result of any line, and if the logic AND operation result is high level, indicating that the line has a ground fault.
As a preferred embodiment, the method of the present application further comprises:
and outputting and displaying the comparison result of each circuit of the low-current grounding power distribution network system.
As a preferred embodiment, the method of the present application further comprises:
the phase voltages and currents of the lines during the operation of the system are output and displayed.
As a preferred implementation mode, the simulation of the occurrence of single-phase earth faults on the low-current grounding distribution network system circuit is specifically as follows:
adding an analog single-phase ground fault controlled by a logic time control model into the built system circuit of the low-current ground distribution network;
the logic time control model is capable of controlling the onset and duration of single phase ground faults.
On the other hand, the application provides a single-phase earth fault line selection system of a low-current grounding system of a micro-grid power distribution network, which comprises the following components:
the model building unit is used for building a small-current grounding power distribution network system comprising a micro-grid;
the fault simulation unit is used for simulating the occurrence of single-phase grounding faults on the low-current grounding power distribution network system line;
the signal acquisition unit is used for acquiring the voltage and the current of each circuit when the small-current grounded power distribution network system operates;
the calculation unit calculates zero sequence components of all the lines of the low-current grounding power distribution network system according to the collected voltages and currents of all the lines;
the extraction unit is used for extracting fifth harmonic components of zero sequence components of all lines in the low-current grounded power distribution network system;
and the line selection unit is used for comparing and selecting the amplitude, the phase and the polarity of the fifth harmonic component respectively, and integrating the amplitude, the phase and the polarity to compare and select the line result to perform fault line selection.
Compared with the prior art, the application has the following advantages and beneficial effects:
1. the application provides a small-current grounding system single-phase grounding fault line selection technology for a micro-grid power distribution network, which is characterized in that three-phase voltage and three-phase current waveforms of each line are monitored in real time when the micro-grid power distribution network operates, zero sequence fault characteristics of each line are extracted, high-order harmonic characteristics of the zero sequence fault characteristics of each line are rapidly extracted by utilizing an FFT algorithm, fifth harmonics in the zero sequence characteristic high-order harmonics are extracted by utilizing a fifth harmonic method to perform fault characteristic contrast line selection, and finally, line selection results of amplitude, phase and polarity of fifth harmonic fault characteristic components are comprehensively compared, so that single-phase grounding fault line selection of the micro-grid power distribution network can be rapidly and accurately realized, and technical support is provided for safe and stable operation of the micro-grid power distribution network;
2. the traditional line selection scheme based on steady-state fault components when a power distribution network system breaks down is only suitable for specific situations, and errors or disturbance can occur in line selection results of certain line selection technologies in a neutral point through arc suppression coil grounding system; the application introduces fast Fourier transformation to extract higher harmonic wave, and extracts the fifth harmonic wave component of fault characteristic based on the fifth harmonic wave method, and experiments prove that the application is applicable to single-phase grounding fault line selection under the condition that neutral point is grounded through arc suppression coil.
Drawings
The accompanying drawings, which are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:
FIG. 1 is a schematic flow chart of a method according to an embodiment of the application;
FIG. 2 is a topological diagram of a power distribution network system model constructed according to an embodiment of the application;
FIG. 3 is a schematic block diagram of a zero sequence component measurement in an embodiment of the application;
FIG. 4 is a fifth harmonic phasor diagram of a non-faulty line and a faulty line in a system; wherein (a) is a non-faulty line; (b) is a faulty wire;
fig. 5 is a schematic block diagram of a comparison module according to an embodiment of the present application.
Fig. 6 is a system schematic block diagram of an embodiment of the present application.
Detailed Description
For the purpose of making apparent the objects, technical solutions and advantages of the present application, the present application will be further described in detail with reference to the following examples and the accompanying drawings, wherein the exemplary embodiments of the present application and the descriptions thereof are for illustrating the present application only and are not to be construed as limiting the present application.
Examples:
the single-phase grounding fault line selection technology of the low-current grounding system applied in the existing power system is mainly divided into a line selection method based on a steady-state component, a line selection method based on a transient component and an external injection method, wherein the line selection method based on the transient component is difficult to accurately grasp the transient process of the grounding fault of the power distribution network due to the fact that the transient process is short; the universality and the practicability of the external injection method are not high; the line selection method based on the steady-state component is based on the fault signal of the single-phase ground fault; therefore, the existing single-phase earth fault line selection technology of the power system is not suitable for the situation that a micro-grid power distribution network exists in two-way power flow. Based on the above, the embodiment provides a single-phase ground fault line selection method of a small-current ground system of a micro-grid power distribution network, and the embodiment provides a single-phase ground fault line selection technology special for the micro-grid power distribution network, which extracts the higher harmonic characteristics of the zero sequence fault characteristics through an FFT algorithm, extracts the five harmonics in the zero sequence characteristic higher harmonics by utilizing a five-harmonic method to perform fault characteristic comparison line selection, and finally comprehensively compares the amplitude, phase and polarity line selection results of the five-harmonic fault characteristic components, so that the single-phase ground fault line selection of the micro-grid power distribution network can be accurately and rapidly realized, and technical support is provided for safe and stable operation of the micro-grid power distribution network.
As shown in fig. 1, the line selection method provided in this embodiment specifically includes the following steps:
step 1, constructing a small-current grounding power distribution network system containing a micro-grid.
In electromagnetic simulation softwareA low-voltage class low-current grounded distribution network is established in a simulation environment. Preferably, a 10kV voltage level can be used from the power source S 1 Three lines which are respectively composed of two groups of overhead lines with the lengths of 20km, 30km and 41km are respectively led out, the voltage levels of the three lines are the same and are 10kV, and the three lines are connected with different loads; the first circuit is connected with another power source S with the same voltage level near the load side transformer 2 I.e. a microgrid, as shown in fig. 2.
And 2, simulating occurrence of single-phase earth faults on a system line.
Adding analog single-phase ground faults controlled by a logic time control model, namely Fault1, fault2 and Fault3, into a built circuit of a low-current grounding distribution network with a micro-grid low voltage level, wherein the logic time control model can control the starting and lasting time of the single-phase ground faults; the topology model, related modeling parameters and single-phase grounding fault preset positions of the system are shown in fig. 2.
And step 3, collecting the voltage and current of each circuit when the system operates.
The output element in the electromagnetic simulation software and the waveform display element cooperate with each phase of voltage and current when the real-time display system operates.
And 4, calculating zero sequence components of each line of the system.
The occurrence of positive sequence, negative sequence and zero sequence is to analyze that when the asymmetry phenomenon occurs in the system voltage and current, the asymmetric components of the three phases are decomposed into symmetric components and equidirectional zero sequence components; these three components can be resolved as long as they are three-phase systems. For an ideal power system, the values of the negative sequence and the zero sequence components are zero due to three-phase symmetry, and the condition of generating zero sequence current is as follows: no matter the longitudinal fault or the transverse fault, or the asymmetry in normal state and abnormal state, the zero sequence current can be generated as long as the zero sequence voltage is generated and the zero sequence current has a passage.
The adder and the multiplier cooperate to calculate the zero sequence voltage and zero sequence current of each line; the output element and the waveform display are matched to realize zero sequence voltage and zero sequence current of each phase when the display system operates; the zero sequence component calculation module built in the electromagnetic simulation software is shown in fig. 3, wherein IA, IB and IC are A, B, C three-phase currents of a certain line in the system respectively, I0 is zero sequence current, the sum of the three-phase currents is multiplied by one third, the calculation of the zero sequence voltage is the same as the zero sequence current calculation principle, namely, the zero sequence voltage is equal to the sum of the three-phase voltages multiplied by one third, and the details are omitted.
And 5, extracting fifth harmonic components of the zero sequence components of each line in the system.
The method adopts an FFT algorithm to analyze higher harmonics of zero sequence components, and uses an FFT module in electromagnetic simulation software to extract fifth harmonics of the zero sequence components of each line in the system.
When the small current system is grounded through the arc suppression coil, the power frequency characteristic is removed, and a large amount of higher harmonic components exist at the same time. Harmonic components in the power system are mainly odd harmonics, and the influence of the arc suppression coil on fault components is reduced along with the increase of harmonic numbers; therefore, the fifth harmonic characteristic is extracted for subsequent line selection analysis.
Fifth harmonic component of non-faulty line:
wherein i= … n; i is not equal to j, I Ai ,I Bi ,I Ci Is the fifth harmonic component of the A, B, C phase current of line I, I 0i The fifth harmonic component of the zero sequence current of line i; the phasor diagram is shown in fig. 4 (a).
Fifth harmonic component of faulty line:
wherein k= … n; k is not equal to j; i Aj 、I Bj 、I Cj The fifth harmonic component of the A, B, C phase current of line j, respectively; i L Compensating current for inductance generated by the arc suppression coil; i 0j The fifth harmonic component of the zero sequence current of line j; the phasor diagram is shown in fig. 4 (b).
According to the principle, the difference of the fifth harmonic components of the non-fault line and the fault line is obvious, so that the embodiment can effectively and reliably select the fault line based on the fifth harmonic components.
And 6, comparing and selecting lines of the amplitude, the phase and the polarity of the fifth harmonic component respectively, and integrating the amplitude, the phase and the polarity to obtain a line selection result for fault line selection.
When a single-phase earth fault occurs in the low-current grounding system, the zero sequence component of the low-current grounding system has the following fault characteristics: the zero sequence current effective value of the fault line is the maximum value; the zero-sequence current phase of the fault line lags the zero-sequence voltage by 90 DEG, and the zero-sequence current of the non-fault line leads the zero-sequence voltage by 90 DEG; the zero sequence current of the failed phase is of opposite polarity to the zero sequence current of the non-failed phase.
The embodiment adopts a comprehensive comparison line selection method of a group comparison amplitude comparison phase method and a polarity comparison method, compares the amplitude of the five-order harmonic of the zero-sequence current of each line, compares the phase of the five-order harmonic of the zero-sequence current of each line and the zero-sequence voltage, and compares the polarity of the five-order harmonic of the zero-sequence current of each line and the zero-sequence voltage. The amplitude, phase and polarity comparison module is built by the electromagnetic simulation software element, the extracted fault characteristic fifth harmonic is compared and selected, wherein the comparison module is built by the logic control module combination in the electromagnetic simulation software simulation environment, and the comparison principle is as shown in fig. 5: the amplitude, phase or polarity of the fifth harmonic component of all the lines in the system are compared in pairs, then the comparison result of the same line is subjected to logic AND operation, if the logic AND result is high level, the amplitude, phase or polarity of the same line is abnormal, as shown in fig. 5, it should be noted that the line selection output principle of the amplitude, phase or polarity comparison module is the same, and the comparison result of the line 1 and the line 2 and the line 1 and the line 3 is compared by taking the system formed by the three lines as an example, and the comparison result of the line 1 is output by logic AND. It should be noted that fig. 5 is only an exemplary illustration, and is not limited to the number of lines and the number of comparison units and logic units in the corresponding comparison module.
When a fault exists in the line, the corresponding line selection module outputs a continuous high level when the single-phase grounding fault occurs in the system, and when the fault does not exist in the line, the corresponding line selection module outputs a continuous low level when the single-phase grounding fault occurs in the system during normal operation; therefore, the embodiment synthesizes three line selection results, namely, the output result of the amplitude, phase and polarity comparison module of a certain line in the system is logically and operated, the result is taken as the final line selection result, if the three comparison modules output high level, the final comprehensive line selection result is also high level, namely, single-phase grounding faults exist in the corresponding line; if one of the three comparison modules outputs a low level, the final comprehensive line selection result is a low level, namely, the corresponding line has no fault and operates normally.
The output element and the waveform display element output the line selection result of the embodiment, and the time at which each line of the power distribution network system has a single-phase ground fault can be judged by observing whether the waveform finally output by the system is at a high level.
Based on the same technical concept, the embodiment also provides a single-phase earth fault line selection system of a small-current grounding system of a micro-grid power distribution network, and the system specifically comprises the following components:
the model building unit is used for building a small-current grounding power distribution network system comprising a micro-grid;
the fault simulation unit is used for simulating the occurrence of single-phase grounding faults on a low-current grounding distribution network system line;
the signal acquisition unit is used for acquiring the voltage and the current of each circuit when the low-current grounded power distribution network system operates;
the calculation unit calculates zero sequence components of all the lines of the low-current grounding power distribution network system according to the collected voltages and currents of all the lines;
the extraction unit is used for extracting fifth harmonic components of zero sequence components of all lines in the low-current grounded power distribution network system;
and the line selection unit is used for comparing and selecting the amplitude, the phase and the polarity of the fifth harmonic component respectively, and integrating the amplitude, the phase and the polarity to select the line and perform fault line selection.
The simulation verification is performed on the method and the system provided by the embodiment, wherein the single-phase grounding fault is set on the third line of the built power distribution network system, the line selection result shown in the table 1 is obtained, and when the single-phase grounding fault exists on the third line of the system, the final output of the three line selection modules is high level, which indicates that the single-phase grounding fault exists on the third line in the system.
TABLE 1
Table 2 shows the applicability comparison of the line selection method proposed in this embodiment with the conventional line selection method based on the steady-state fault characteristics of the system under different grounding types; the traditional line selection method is applicable to a neutral point ungrounded system and a neutral point high-resistance grounded system, but in a neutral point arc suppression coil grounded system, misoperation or disturbance can occur to a line selection result, stability and accuracy are not high enough, and robustness is not strong; the line selection method provided by the embodiment is simultaneously applicable to three different grounding types of systems, and has high accuracy, sensitivity and robustness.
TABLE 2
As can be seen from the above table, compared with the conventional line selection scheme, the scheme used in the present application is applicable to three common grounding types, and has stronger robustness. Meanwhile, in the micro-grid power distribution network, a single traditional line selection scheme may be interfered by bidirectional tide to cause low line selection rapidness and robustness, and the scheme used in the application integrates a plurality of line selection schemes, extracts fifth harmonic waves of fault components for comparison, and comprehensively compares the five harmonic waves from a plurality of aspects such as amplitude, phase and polarity, so that the accuracy and the robustness of line selection are completely superior to those of the single traditional line selection scheme.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the application, and is not meant to limit the scope of the application, but to limit the application to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the application are intended to be included within the scope of the application.
Claims (10)
1. The utility model provides a little electric current earth system single phase earth fault route selection method of micro-grid distribution network which characterized in that, the method includes:
constructing a small-current grounding power distribution network system containing a micro-grid;
simulating occurrence of single-phase earth faults on the small-current grounded power distribution network system line;
collecting the voltage and current of each circuit when the small-current grounding power distribution network system operates;
calculating zero sequence components of all the lines of the small-current grounding power distribution network system according to the collected voltages and currents of all the lines;
extracting fifth harmonic components of zero sequence components of all lines in the small-current grounding power distribution network system;
and respectively comparing and selecting the amplitude, the phase and the polarity of the fifth harmonic component, and integrating amplitude, phase and polarity comparison and selecting results to perform fault line selection.
2. The method for selecting single-phase earth faults of the low-current grounding system of the micro-grid power distribution network according to claim 1 is characterized by constructing the low-current grounding power distribution network system comprising the micro-grid and specifically comprising the following steps:
three lines are respectively led out from a power supply, the voltage levels of the three lines are the same and are 10kV, and the three lines are connected with different loads;
and connecting another power source with the same voltage level, namely a micro-grid, to the position of the first line close to the load side transformer.
3. The method for selecting a single-phase earth fault line of a small-current grounding system of a micro-grid power distribution network according to claim 1, wherein the zero sequence component of each line is calculated, specifically:
constructing a zero sequence voltage calculation module and a zero sequence current calculation module by the adder and the multiplier;
wherein the zero sequence current is equal to the sum of three currents of the three phases multiplied by one third, and the zero sequence voltage is equal to the sum of three voltages of the three phases multiplied by one third.
4. The method for selecting the single-phase earth fault line of the low-current grounding system of the micro-grid power distribution network according to claim 1, wherein the fifth harmonic component of the zero sequence component of each line is extracted by adopting an FFT algorithm.
5. The method for selecting a single-phase earth fault line of a small-current grounding system of a micro-grid power distribution network according to any one of claims 1 to 4, wherein the comparing and selecting the line of the amplitude, the phase and the polarity of the fifth harmonic component is performed respectively, specifically:
comparing the amplitude, phase or polarity of the fifth harmonic components of all lines in the system in pairs;
and then performing logic AND operation on all relevant comparison results of the same circuit, and if the logic AND result is high level, indicating that the amplitude, the phase or the polarity of the circuit is abnormal.
6. The method for selecting a single-phase earth fault line of a small-current grounding system of a micro-grid power distribution network according to claim 5, wherein the fault line selection is performed by combining amplitude, phase and polarity comparison line selection results, and specifically comprises the following steps:
and performing logic AND operation on the amplitude, phase and polarity comparison result of any line, and if the logic AND operation result is high level, indicating that the line has a ground fault.
7. A method for selecting a single-phase ground fault line for a low-current grounding system of a micro-grid power distribution network according to claim 1, wherein said method further comprises:
and outputting and displaying the comparison result of each circuit of the low-current grounding power distribution network system.
8. A method for selecting a single-phase ground fault line for a low-current grounding system of a micro-grid power distribution network according to claim 1, wherein said method further comprises:
the phase voltages and currents of the lines during the operation of the system are output and displayed.
9. The method for selecting a single-phase ground fault line of a small-current grounding system of a micro-grid power distribution network according to claim 1, wherein the occurrence of the single-phase ground fault is simulated on a line of the small-current grounding power distribution network system, specifically:
adding an analog single-phase ground fault controlled by a logic time control model into the built system circuit of the low-current ground distribution network;
the logic time control model is capable of controlling the onset and duration of single phase ground faults.
10. A small current grounding system single-phase earth fault line selection system of a micro-grid power distribution network, characterized in that the system comprises:
the model building unit is used for building a small-current grounding power distribution network system comprising a micro-grid;
the fault simulation unit is used for simulating the occurrence of single-phase grounding faults on the low-current grounding power distribution network system line;
the signal acquisition unit is used for acquiring the voltage and the current of each circuit when the small-current grounded power distribution network system operates;
the calculation unit calculates zero sequence components of all the lines of the low-current grounding power distribution network system according to the collected voltages and currents of all the lines;
the extraction unit is used for extracting fifth harmonic components of zero sequence components of all lines in the low-current grounded power distribution network system;
and the line selection unit is used for comparing and selecting the amplitude, the phase and the polarity of the fifth harmonic component respectively, and integrating the amplitude, the phase and the polarity to compare and select the line result to perform fault line selection.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117805554A (en) * | 2023-12-29 | 2024-04-02 | 国网四川省电力公司电力科学研究院 | Transient line selection method and system for single-phase earth fault of power distribution network ring network |
| CN117973097A (en) * | 2024-04-02 | 2024-05-03 | 国网四川省电力公司电力科学研究院 | Method for acquiring resistance interval corresponding to starting fixed value under arc suppression coil grounding system |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117805554A (en) * | 2023-12-29 | 2024-04-02 | 国网四川省电力公司电力科学研究院 | Transient line selection method and system for single-phase earth fault of power distribution network ring network |
| CN117973097A (en) * | 2024-04-02 | 2024-05-03 | 国网四川省电力公司电力科学研究院 | Method for acquiring resistance interval corresponding to starting fixed value under arc suppression coil grounding system |
| CN117973097B (en) * | 2024-04-02 | 2024-06-11 | 国网四川省电力公司电力科学研究院 | Method for acquiring resistance interval corresponding to starting fixed value under arc suppression coil grounding system |
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