CN117054812A - Method, device, equipment and medium for detecting single-phase earth fault of power distribution network - Google Patents
Method, device, equipment and medium for detecting single-phase earth fault of power distribution network Download PDFInfo
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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
- 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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Abstract
The application relates to a method, a device, equipment and a medium for detecting single-phase earth faults of a power distribution network, wherein the method comprises the following steps: collecting zero sequence voltage and zero sequence current in real time; judging whether to enter a line fault judging process or not based on the zero sequence voltage, the zero sequence current and the set abrupt starting value; when a line fault judging process is entered, recording a starting point of occurrence of the line fault; acquiring a zero sequence voltage signal and a zero sequence current signal of a previous period and a next period of the line fault; calculating zero-sequence reactive power according to the zero-sequence voltage signal and the zero-sequence current signal; calculating a zero sequence voltage effective value of a preset period after a fault occurs; and judging whether the line fault is a single-phase grounding fault or not according to the zero-sequence reactive power and the zero-sequence voltage effective value of a preset period after the fault occurs. The application improves the single-phase earth fault detection accuracy.
Description
Technical Field
The application relates to the technical field of single-phase earth fault detection and identification of power distribution networks, in particular to a single-phase earth fault detection method and device of a power distribution network.
Background
The neutral point of the domestic 10kV power distribution network mainly has 3 grounding modes of ungrounded resonance grounding (also called arc suppression coil grounding) and low-resistance grounding (also called small-resistance grounding). Among them, ungrounded systems (accounting for 60% or more of the total) and resonant grounded systems (accounting for about one third) are most widely used, collectively referred to as low current grounded systems. The small-current grounding system has the advantages of small fault current, automatic extinction of transient fault arc, 2 hours of operation of the system with grounding point, high power supply reliability, small contact voltage and step voltage caused by grounding fault and the like; on the other hand, long-time grounding operation may cause problems such as inter-phase short-circuit failure, cable pit ignition, etc. The operation regulations of the distribution network are modified by the national power grid company and the southern power grid company, and the permanent low-current ground fault is required to be isolated quickly, so that the risk of accident expansion is eliminated, the power supply safety and reliability are further improved, and development opportunities and challenges are brought to the low-current ground fault detection technology.
The single-phase earth fault detection technology of the low-current grounding system is mainly influenced by factors such as a neutral point grounding mode, a power distribution network scale, a grounding transitional resistance and the like, and a steady-state calculation method such as a zero-sequence reactive power direction method and a zero-sequence active power direction method is mainly adopted in the early stage, but the steady-state calculation method is generally applicable to grounding faults when an ungrounded system or the transitional resistance is lower; when single-phase earth faults occur, transient components are more obvious than steady-state components, the contained fault information is more abundant, and the influence of arc suppression coils is smaller.
The prior patent document CN103954876A discloses a distribution network single-phase grounding fault detection method based on transient components, and when the system is grounded in a high-resistance mode, the terminal cannot capture the transient process of fault occurrence due to the fact that the zero sequence voltage is low at the beginning of fault occurrence and the terminal cannot capture the transient process of fault occurrence due to the fact that the zero sequence voltage is simply relied on, so that the accuracy of fault judgment is affected. The method can not accurately identify single-phase earth faults exceeding 1kΩ transition resistance, and the amplitude of harmonic component in actual earth fault current is smaller (generally less than 10% of power frequency current) and unstable, so the protection method using 5 th harmonic component has low reliability. In addition, the method needs to calculate the capacitance to ground parameter of the distribution line, but the single-phase earth fault can generate high-frequency zero sequence voltage and current, which can influence the accuracy of parameter identification.
Disclosure of Invention
The application aims to solve the technical problem of providing a single-phase earth fault detection method and device for a power distribution network, and the single-phase earth fault detection accuracy is improved.
The technical scheme adopted for solving the technical problems is as follows: the utility model provides a distribution network single-phase earth fault detection method, which comprises the following steps:
collecting zero sequence voltage and zero sequence current in real time;
judging whether to enter a line fault judging process or not based on the zero sequence voltage, the zero sequence current and the set abrupt starting value;
when a line fault judging process is entered, recording a starting point of occurrence of the line fault;
acquiring a zero sequence voltage signal and a zero sequence current signal of a previous period and a next period of the line fault;
calculating zero-sequence reactive power according to the zero-sequence voltage signal and the zero-sequence current signal;
calculating a zero sequence voltage effective value of a preset period after a fault occurs;
and judging whether the line fault is a single-phase grounding fault or not according to the zero-sequence reactive power and the zero-sequence voltage effective value of a preset period after the fault occurs.
The judging whether to enter a line fault judging process based on the zero sequence voltage, the zero sequence current and the set abrupt start value specifically comprises the following steps:
respectively calculating a sudden change value of the zero sequence voltage and a sudden change value of the zero sequence current according to the acquired zero sequence voltage and zero sequence current;
judging whether the abrupt change value of the zero sequence voltage is larger than a voltage abrupt change starting value;
if the abrupt change value of the zero sequence voltage is larger than the voltage abrupt change starting value, judging whether the abrupt change value of the zero sequence current is larger than the current abrupt change starting value;
if the abrupt change value of the zero sequence current is not larger than the current abrupt change starting value, judging whether the maximum value of the zero sequence current in two periods after the fault exceeds the maximum value of the current;
if the abrupt change value of the zero sequence current is larger than the current abrupt change starting value or the zero sequence current maximum value of the two periods after the fault exceeds the current maximum value, judging whether the zero sequence voltage effective value of the first period before the fault is smaller than a voltage effective value threshold value;
if the zero sequence voltage effective value of the first period before the fault is smaller than the voltage effective value threshold, judging whether the zero sequence voltage effective value of the third period after the fault is larger than the voltage effective value threshold;
if the zero sequence voltage effective value of the third period after the fault is greater than the voltage effective value threshold, entering a line fault judging flow.
The single-phase earth fault detection method of the power distribution network further comprises the following steps: and when the abrupt change value of the zero sequence voltage is not larger than the voltage abrupt change starting value, or the zero sequence current maximum value of the two periods after the fault does not exceed the current maximum value, or the zero sequence voltage effective value of the first period before the fault is not smaller than the voltage effective value threshold, or the zero sequence voltage effective value of the third period after the fault is not larger than the voltage effective value threshold, the zero sequence voltage and the zero sequence current are collected again.
The voltage jump starting value is 3% of the rated voltage of the system, and the voltage effective value threshold is 8% of the rated voltage of the system.
The calculating the zero-sequence reactive power according to the zero-sequence voltage signal and the zero-sequence current signal specifically comprises the following steps:
band-pass filtering the zero sequence voltage signal and the zero sequence current signal;
and performing Hilbert transformation on the zero-sequence voltage signal and the zero-sequence current signal after the filtering treatment, and calculating the zero-sequence reactive power.
The filtering-processed zero-sequence voltage signal and zero-sequence current signal are subjected to Hilbert transformation, and zero-sequence reactive power is calculated, and the method specifically comprises the following steps:
the zero sequence voltage signal after the filtering treatment passes through a first Hilbert phase-shifting filter bank to obtain a first phase-shifting voltage signal F1 and a second phase-shifting voltage signal F2;
the zero sequence current signal after the filtering treatment passes through a second Hilbert phase-shifting filter bank to obtain a first phase-shifting current signal F3 and a second phase-shifting current signal F4;
and calculating a reactive power signal based on the first phase-shifting voltage signal F1, the second phase-shifting voltage signal F2, the first phase-shifting current signal F3 and the second phase-shifting current signal F4, and obtaining the zero sequence reactive power through low-pass filtering of the reactive power signal.
The first and second hilbert phase-shifting filter banks each include a first and second hilbert phase-shifting filter; the transfer function of the first hilbert phase-shifting filter has the form:the method comprises the steps of carrying out a first treatment on the surface of the The transfer function of the second hilbert phase-shifting filter has the form: />Wherein, the method comprises the steps of, wherein,H 1 (z) Representing the transfer function of the first hilbert phase-shifting filter,H 2 (z) Representing the transfer function of the second hilbert phase-shifting filter,zrepresenting a discrete z-transform,a i representing the hilbert filter coefficients.
The reactive power signal is calculated by q (i) =0.5 [ F1 x F4-F2 x F3], where q (i) represents the reactive power signal.
The step of judging whether the line fault is a single-phase earth fault according to the zero-sequence reactive power and the zero-sequence voltage effective value of a preset period after the fault occurs, specifically comprises the following steps:
judging whether the zero sequence reactive power is a positive value or not;
when the zero sequence reactive power is a positive value, judging whether the zero sequence voltage effective value of the preset period after the fault occurs is larger than a voltage effective value threshold value or not;
and when the zero sequence voltage effective value of the preset period after the fault occurs is larger than a voltage effective value threshold value, judging that the line fault is a single-phase grounding fault.
The technical scheme adopted for solving the technical problems is as follows: provided is a single-phase earth fault detection device for a power distribution network, comprising:
the data acquisition module is used for acquiring zero-sequence voltage and zero-sequence current in real time;
the first judging module is used for judging whether to enter a line fault judging process or not based on the zero sequence voltage, the zero sequence current and the set abrupt starting value;
the recording module is used for recording the starting point of the occurrence of the line fault when entering the line fault judging process;
the acquisition module is used for acquiring a zero sequence voltage signal and a zero sequence current signal of a previous period and a next period of the line fault;
the first calculation module is used for calculating zero-sequence reactive power according to the zero-sequence voltage signal and the zero-sequence current signal;
the second calculation module is used for calculating the zero sequence voltage effective value of a preset period after the fault occurs;
and the second judging module is used for judging whether the line fault is a single-phase grounding fault or not according to the zero-sequence reactive power and the zero-sequence voltage effective value of the preset period after the fault occurs.
The technical scheme adopted for solving the technical problems is as follows: an electronic device is provided, comprising a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor realizes the steps of the single-phase earth fault detection method of the power distribution network when executing the computer program.
The technical scheme adopted for solving the technical problems is as follows: there is provided a computer readable storage medium having stored thereon a computer program which when executed by a processor implements the steps of the power distribution network single phase earth fault detection method described above.
Advantageous effects
Due to the adoption of the technical scheme, compared with the prior art, the application has the following advantages and positive effects: the application realizes the accurate capturing of the transient process of the single-phase earth fault at the beginning by combining the zero sequence voltage and the zero sequence current abrupt change information of the single-phase earth fault at the beginning, and provides an accurate fault starting point for the subsequent fault judging algorithm. According to the application, the primary zero-sequence voltage and zero-sequence current generated by the single-phase grounding fault are subjected to band-pass filtering, the filtered data are subjected to reactive power calculation, the internal fault or the external fault is judged by utilizing the direction of the reactive power, the single-phase grounding fault with the grounding transition resistance within 5k omega can be accurately identified, and the single-phase grounding fault is not influenced by an arc suppression coil. The transient zero sequence reactive power is calculated through the two pairs of Hilbert phase-shifting filters, the calculated amount is small, the real-time performance is high, the precision is high, and the reliability of the ground fault direction detection is further ensured.
Drawings
Fig. 1 is a flowchart of a method for detecting a single-phase earth fault of a power distribution network according to a first embodiment of the present application;
fig. 2 is a schematic diagram of a reactive power calculation method in a first embodiment of the present application.
Detailed Description
The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the teachings of the present application, and such equivalents are intended to fall within the scope of the application as defined in the appended claims.
The first embodiment of the application relates to a single-phase earth fault detection method of a power distribution network, as shown in fig. 1, comprising the following steps:
and step 1, collecting zero sequence voltage and zero sequence current in real time. In the step, the power distribution terminal, the zero-sequence voltage sensor and the zero-sequence current transformer can be arranged on the power distribution line, and the power distribution terminal is utilized to synchronously collect and capture the zero-sequence voltage and the zero-sequence current in the initial transient process of the line fault.
And 2, judging whether to enter a line fault judging process or not based on the zero sequence voltage, the zero sequence current and the set abrupt start value, wherein the step specifically comprises the following steps:
respectively calculating a sudden change value of the zero sequence voltage and a sudden change value of the zero sequence current according to the acquired zero sequence voltage and zero sequence current;
judging whether the abrupt change value of the zero sequence voltage is larger than a voltage abrupt change starting value; in this embodiment, the voltage jump starting value is 3% of the rated voltage of the system.
If the abrupt change value of the zero sequence voltage is larger than the voltage abrupt change starting value, judging whether the abrupt change value of the zero sequence current is larger than the current abrupt change starting value;
if the abrupt change value of the zero sequence current is not larger than the current abrupt change starting value, judging whether the maximum value of the zero sequence current in two periods after the fault exceeds the maximum value of the current;
if the abrupt change value of the zero sequence current is larger than the current abrupt change starting value or the zero sequence current maximum value of the two periods after the fault exceeds the current maximum value, judging whether the zero sequence voltage effective value of the first period before the fault is smaller than a voltage effective value threshold value; the voltage effective value threshold value in the embodiment is 8% of the rated voltage of the system;
if the zero sequence voltage effective value of the first period before the fault is smaller than the voltage effective value threshold, judging whether the zero sequence voltage effective value of the third period after the fault is larger than the voltage effective value threshold;
if the zero sequence voltage effective value of the third period after the fault is greater than the voltage effective value threshold, entering a line fault judging flow.
It is worth mentioning that the zero sequence voltage and zero sequence current are re-collected when any one of the following conditions occurs:
the abrupt change value of the zero sequence voltage is not more than the voltage abrupt change starting value;
the zero sequence current maximum value of the two periods after the fault does not exceed the current maximum value;
the zero sequence voltage effective value of the first period before the fault is not less than the voltage effective value threshold value;
and the effective value of the zero sequence voltage in the third period after the fault is not more than the threshold value of the effective value of the voltage.
And step 3, recording the starting point of the occurrence of the line fault when entering a line fault judging process.
And 4, acquiring a zero sequence voltage signal and a zero sequence current signal of a previous period and a next period of the line fault based on the starting point of the line fault.
And 5, calculating zero-sequence reactive power according to the zero-sequence voltage signal and the zero-sequence current signal, wherein the method specifically comprises the following steps of:
band-pass filtering the zero sequence voltage signal and the zero sequence current signal; the filtering frequency of the band-pass filtering in the step is 155Hz-600Hz.
And performing Hilbert transformation on the zero-sequence voltage signal and the zero-sequence current signal after the filtering treatment, and calculating the zero-sequence reactive power. Specifically, as shown in fig. 2, the zero sequence voltage signal after the filtering process is passed through a first hilbert phase-shifting filter bank to obtain a first phase-shifting voltage signal F1 and a second phase-shifting voltage signal F2; the zero sequence current signal after the filtering treatment passes through a second Hilbert phase-shifting filter bank to obtain a first phase-shifting current signal F3 and a second phase-shifting current signal F4; and calculating a reactive power signal based on the first phase-shifting voltage signal F1, the second phase-shifting voltage signal F2, the first phase-shifting current signal F3 and the second phase-shifting current signal F4, and obtaining the zero sequence reactive power through low-pass filtering of the reactive power signal.
Wherein the first and second banks of Hilbert phase-shifting filters each include a first Hilbert phase-shifting filter and a second Hilbert phase-shifting filter; the first Hilbert phase-shifting filter and the second Hilbert phase-shifting filter are IIR type Hilbert phase-shifting filters designed by half-band filters. The transfer function of the first hilbert phase-shifting filter is in the form of:the method comprises the steps of carrying out a first treatment on the surface of the The transfer function of the second hilbert phase-shift filter is in the form of: />Wherein, the method comprises the steps of, wherein,H 1 (z) Representing the transfer function of the first hilbert phase-shifting filter,H 2 (z) Representing the transfer function of the second hilbert phase-shifting filter,zrepresenting a discrete z-transform,a i representing the hilbert filter coefficients.
In calculating the reactive power signal, the reactive power signal q (i) is calculated by q (i) =0.5 [ F1 x F4-F2 x F3 ]. The transient zero sequence reactive power is calculated through the two pairs of Hilbert phase-shifting filters, the calculated amount is small, the real-time performance is strong, the precision is high, and the reliability of the ground fault direction detection is further ensured.
Step 6, calculating a zero sequence voltage effective value of a preset period after the fault occurs; the preset period in this embodiment is 4-6 periods after the occurrence of the fault.
And step 7, judging whether the line fault is a single-phase earth fault or not according to the zero-sequence reactive power and the zero-sequence voltage effective value of a preset period after the fault occurs, wherein the method specifically comprises the following steps:
judging whether the zero sequence reactive power is a positive value or not;
when the zero sequence reactive power is a positive value, judging whether the zero sequence voltage effective value of the preset period after the fault occurs is larger than a voltage effective value threshold value or not;
and when the zero sequence voltage effective value of the preset period after the fault occurs is larger than a voltage effective value threshold value, judging that the line fault is a single-phase grounding fault.
It is easy to find that the application realizes the accurate capturing of the transient process of the single-phase earth fault at the beginning by combining the initial zero-sequence voltage and zero-sequence current mutation information of the single-phase earth fault, and provides an accurate fault starting point for the subsequent fault judging algorithm. According to the application, the primary zero-sequence voltage and zero-sequence current generated by the single-phase grounding fault are subjected to band-pass filtering, the filtered data are subjected to reactive power calculation, the internal fault or the external fault is judged by utilizing the direction of the reactive power, the single-phase grounding fault with the grounding transition resistance within 5k omega can be accurately identified, and the single-phase grounding fault is not influenced by an arc suppression coil.
A second embodiment of the present application relates to a single-phase earth fault detection device for a power distribution network, including:
the data acquisition module is used for acquiring zero-sequence voltage and zero-sequence current in real time;
the first judging module is used for judging whether to enter a line fault judging process or not based on the zero sequence voltage, the zero sequence current and the set abrupt starting value;
the recording module is used for recording the starting point of the occurrence of the line fault when entering the line fault judging process;
the acquisition module is used for acquiring a zero sequence voltage signal and a zero sequence current signal of a previous period and a next period of the line fault;
the first calculation module is used for calculating zero-sequence reactive power according to the zero-sequence voltage signal and the zero-sequence current signal;
the second calculation module is used for calculating the zero sequence voltage effective value of a preset period after the fault occurs;
and the second judging module is used for judging whether the line fault is a single-phase grounding fault or not according to the zero-sequence reactive power and the zero-sequence voltage effective value of the preset period after the fault occurs.
The first judging module includes:
the abrupt change value calculation unit is used for calculating the abrupt change value of the zero sequence voltage and the abrupt change value of the zero sequence current according to the acquired zero sequence voltage and zero sequence current respectively;
the first judging unit is used for judging whether the abrupt change value of the zero sequence voltage is larger than a voltage abrupt change starting value or not;
the second judging unit is used for judging whether the abrupt change value of the zero sequence current is larger than the current abrupt change starting value or not when the abrupt change value of the zero sequence voltage is larger than the voltage abrupt change starting value;
the third judging unit is used for judging whether the maximum value of the zero sequence current in two periods after the fault exceeds the maximum value of the current when the abrupt change value of the zero sequence current is not larger than the abrupt change starting value of the current;
a fourth judging unit, configured to judge whether the zero sequence voltage effective value of the first period before the fault is smaller than a voltage effective value threshold when the abrupt change value of the zero sequence current is greater than a current abrupt change starting value or the zero sequence current maximum value of the two periods after the fault exceeds the current maximum value;
a fifth judging unit, configured to judge whether the zero sequence voltage effective value of the first period before the fault is smaller than the voltage effective value threshold value, and whether the zero sequence voltage effective value of the third period after the fault is greater than the voltage effective value threshold value;
and the judging flow entering unit is used for entering the line fault judging flow when the zero sequence voltage effective value of the third period after the fault is greater than the voltage effective value threshold value.
The first judging module further includes: and the re-acquisition unit is used for re-acquiring the zero sequence voltage and the zero sequence current when the abrupt change value of the zero sequence voltage is not larger than the voltage abrupt change starting value, or the zero sequence current maximum value of the two periods after the fault does not exceed the current maximum value, or the zero sequence voltage effective value of the first period before the fault is not smaller than the voltage effective value threshold, or the zero sequence voltage effective value of the third period after the fault is not larger than the voltage effective value threshold.
The voltage jump starting value is 3% of the rated voltage of the system, and the voltage effective value threshold is 8% of the rated voltage of the system.
The first computing module includes:
the filtering unit is used for carrying out band-pass filtering processing on the zero sequence voltage signal and the zero sequence current signal;
and the reactive power calculation unit is used for performing Hilbert transformation on the zero-sequence voltage signal and the zero-sequence current signal after the filtering processing and calculating the zero-sequence reactive power.
The reactive power calculation unit includes:
the first phase-shifting processing subunit is used for enabling the zero sequence voltage signal after the filtering processing to pass through a first Hilbert phase-shifting filter bank to obtain a first phase-shifting voltage signal F1 and a second phase-shifting voltage signal F2;
the second phase-shifting processing subunit is used for enabling the zero sequence current signal after the filtering processing to pass through a second Hilbert phase-shifting filter bank to obtain a first phase-shifting current signal F3 and a second phase-shifting current signal F4;
and the calculating subunit is used for calculating a reactive power signal based on the first phase-shifting voltage signal F1, the second phase-shifting voltage signal F2, the first phase-shifting current signal F3 and the second phase-shifting current signal F4, and obtaining the zero-sequence reactive power Qval [ n ] through low-pass filtering of the reactive power signal.
The first and second hilbert phase-shifting filter banks each include a first and second hilbert phase-shifting filter; the first HillThe transfer function of the bert phase-shift filter is in the form of:the method comprises the steps of carrying out a first treatment on the surface of the The transfer function of the second hilbert phase-shifting filter has the form: />Wherein, the method comprises the steps of, wherein,H 1 (z) Representing the transfer function of the first hilbert phase-shifting filter,H 2 (z) Representing the transfer function of the second hilbert phase-shifting filter,zrepresenting a discrete z-transform,a i representing the hilbert filter coefficients.
The calculation subunit calculates a reactive power signal by q (i) =0.5 [ F1 x F4-F2 x F3], where q (i) represents the reactive power signal.
The second judging module includes:
a sixth judging unit, configured to judge whether the zero sequence reactive power is a positive value;
a seventh judging unit, configured to judge, when the zero-sequence reactive power is a positive value, whether a zero-sequence voltage effective value of a preset period after the fault occurs is greater than a voltage effective value threshold;
and the judging unit is used for judging that the line fault is a single-phase grounding fault when the zero sequence voltage effective value of the preset period after the fault occurs is greater than a voltage effective value threshold value.
A third embodiment of the application relates to an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, which processor, when executing the computer program, implements the steps of the method for detecting a single phase earth fault of a power distribution network according to the first embodiment.
A fourth embodiment of the application relates to a computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, implements the steps of the power distribution network single-phase earth fault detection method of the first embodiment.
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 scheme in the embodiment of the application can be realized by adopting various computer languages, such as object-oriented programming language Java, an transliteration script language JavaScript and the like.
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.
While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (12)
1. The single-phase earth fault detection method for the power distribution network is characterized by comprising the following steps of:
collecting zero sequence voltage and zero sequence current in real time;
judging whether to enter a line fault judging process or not based on the zero sequence voltage, the zero sequence current and the set abrupt starting value;
when a line fault judging process is entered, recording a starting point of occurrence of the line fault;
acquiring a zero sequence voltage signal and a zero sequence current signal of a previous period and a next period of the line fault;
calculating zero-sequence reactive power according to the zero-sequence voltage signal and the zero-sequence current signal;
calculating a zero sequence voltage effective value of a preset period after a fault occurs;
and judging whether the line fault is a single-phase grounding fault or not according to the zero-sequence reactive power and the zero-sequence voltage effective value of a preset period after the fault occurs.
2. The method for detecting a single-phase earth fault of a power distribution network according to claim 1, wherein the step of determining whether to enter a line fault discrimination process based on the zero sequence voltage, the zero sequence current and the set abrupt start value specifically comprises:
respectively calculating a sudden change value of the zero sequence voltage and a sudden change value of the zero sequence current according to the acquired zero sequence voltage and zero sequence current;
judging whether the abrupt change value of the zero sequence voltage is larger than a voltage abrupt change starting value;
if the abrupt change value of the zero sequence voltage is larger than the voltage abrupt change starting value, judging whether the abrupt change value of the zero sequence current is larger than the current abrupt change starting value;
if the abrupt change value of the zero sequence current is not larger than the current abrupt change starting value, judging whether the maximum value of the zero sequence current in two periods after the fault exceeds the maximum value of the current;
if the abrupt change value of the zero sequence current is larger than the current abrupt change starting value or the zero sequence current maximum value of the two periods after the fault exceeds the current maximum value, judging whether the zero sequence voltage effective value of the first period before the fault is smaller than a voltage effective value threshold value;
if the zero sequence voltage effective value of the first period before the fault is smaller than the voltage effective value threshold, judging whether the zero sequence voltage effective value of the third period after the fault is larger than the voltage effective value threshold;
if the zero sequence voltage effective value of the third period after the fault is greater than the voltage effective value threshold, entering a line fault judging flow.
3. The method for detecting a single-phase earth fault of a power distribution network according to claim 2, further comprising: and when the abrupt change value of the zero sequence voltage is not larger than the voltage abrupt change starting value, or the zero sequence current maximum value of the two periods after the fault does not exceed the current maximum value, or the zero sequence voltage effective value of the first period before the fault is not smaller than the voltage effective value threshold, or the zero sequence voltage effective value of the third period after the fault is not larger than the voltage effective value threshold, the zero sequence voltage and the zero sequence current are collected again.
4. The method for detecting single-phase earth faults of a power distribution network according to claim 2, wherein the voltage jump starting value is 3% of the rated voltage of the system, and the voltage effective value threshold is 8% of the rated voltage of the system.
5. The method for detecting single-phase earth faults of a power distribution network according to claim 1, characterized in that said calculating zero sequence reactive power from said zero sequence voltage signal and zero sequence current signal comprises in particular:
band-pass filtering the zero sequence voltage signal and the zero sequence current signal;
and performing Hilbert transformation on the zero-sequence voltage signal and the zero-sequence current signal after the filtering treatment, and calculating the zero-sequence reactive power.
6. The method for detecting single-phase earth faults of a power distribution network according to claim 5, wherein the performing hilbert transformation on the zero-sequence voltage signal and the zero-sequence current signal after the filtering processing, and calculating the zero-sequence reactive power specifically comprises:
the zero sequence voltage signal after the filtering treatment passes through a first Hilbert phase-shifting filter bank to obtain a first phase-shifting voltage signal F1 and a second phase-shifting voltage signal F2;
the zero sequence current signal after the filtering treatment passes through a second Hilbert phase-shifting filter bank to obtain a first phase-shifting current signal F3 and a second phase-shifting current signal F4;
and calculating a reactive power signal based on the first phase-shifting voltage signal F1, the second phase-shifting voltage signal F2, the first phase-shifting current signal F3 and the second phase-shifting current signal F4, and obtaining the zero sequence reactive power through low-pass filtering of the reactive power signal.
7. The method of claim 6, wherein the first and second hilbert phase-shifting filter banks each comprise a first hilbert phase-shifting filter and a second hilbert phase-shifting filter; the transfer function of the first hilbert phase-shifting filter has the form:the method comprises the steps of carrying out a first treatment on the surface of the The transfer function of the second hilbert phase-shifting filter has the form:wherein, the method comprises the steps of, wherein,H 1 (z) Representing the transfer function of the first hilbert phase-shifting filter,H 2 (z) Representing the transfer function of the second hilbert phase-shifting filter,zrepresenting a discrete z-transform,a i representing the hilbert filter coefficients.
8. The method of claim 6, wherein the reactive power signal is calculated by q (i) = 0.5[ F1 x F4-F2 x F3], wherein q (i) represents the reactive power signal.
9. The method for detecting a single-phase earth fault of a power distribution network according to claim 1, wherein the step of judging whether the line fault is a single-phase earth fault according to the zero-sequence reactive power and a zero-sequence voltage effective value of a preset period after the fault occurs specifically comprises:
judging whether the zero sequence reactive power is a positive value or not;
when the zero sequence reactive power is a positive value, judging whether the zero sequence voltage effective value of the preset period after the fault occurs is larger than a voltage effective value threshold value or not;
and when the zero sequence voltage effective value of the preset period after the fault occurs is larger than a voltage effective value threshold value, judging that the line fault is a single-phase grounding fault.
10. A single-phase earth fault detection device for a power distribution network, comprising:
the data acquisition module is used for acquiring zero-sequence voltage and zero-sequence current in real time;
the first judging module is used for judging whether to enter a line fault judging process or not based on the zero sequence voltage, the zero sequence current and the set abrupt starting value;
the recording module is used for recording the starting point of the occurrence of the line fault when entering the line fault judging process;
the acquisition module is used for acquiring a zero sequence voltage signal and a zero sequence current signal of a previous period and a next period of the line fault;
the first calculation module is used for calculating zero-sequence reactive power according to the zero-sequence voltage signal and the zero-sequence current signal;
the second calculation module is used for calculating the zero sequence voltage effective value of a preset period after the fault occurs;
and the second judging module is used for judging whether the line fault is a single-phase grounding fault or not according to the zero-sequence reactive power and the zero-sequence voltage effective value of the preset period after the fault occurs.
11. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor, when executing the computer program, implements the steps of the power distribution network single-phase earth fault detection method according to any one of claims 1-9.
12. A computer readable storage medium having stored thereon a computer program, which when executed by a processor performs the steps of the power distribution network single phase earth fault detection method according to any of claims 1-9.
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