CN109655713B - Single-phase earth fault positioning method and system - Google Patents
Single-phase earth fault positioning method and system Download PDFInfo
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Abstract
The invention discloses a single-phase earth fault positioning method and a system, wherein the method comprises the steps of collecting fault data collected by each detection device; when fault information is complete after a small current ground fault occurs, judging that the confidence coefficient of a fault study result of a selected detection device meets a specific requirement, judging a single-phase ground fault section by using each fault detection device to obtain a fault section identification result of each fault detection device, and determining a final fault section if the identification results are consistent; and if the fault information of each fault detection device is incomplete or the confidence coefficient of the fault research and judgment result does not meet the specific requirement or the identification results of the fault sections are inconsistent, determining the final fault section by using a correlation coefficient method. The fault detection equipment in the distribution network is utilized to the maximum extent, the small-current grounding fault positioning technology based on multi-source information is realized, and the defect of low precision of the existing fault positioning technology based on single-source information is overcome; the data preprocessing ensures the accuracy and reliability of fault location.
Description
Technical Field
The invention relates to a single-phase earth fault positioning technology, in particular to a single-phase earth fault positioning system and method, and belongs to the technical field of relay protection of power systems.
Background
An important characteristic of the smart grid is that the fault can be automatically detected and corrected, so that the power failure range and the power failure time are reduced to the greatest extent, and the power failure loss of a user is reduced. According to statistics, most of power failure of a power system is caused by the power distribution network, single-phase earth faults account for about 80% of the total number of faults of the power distribution network, and fault detection (line selection, positioning, isolation and the like) technology of the intelligent power distribution network has very important significance for improving power supply reliability and promoting intelligent power grid construction.
The distribution network in China generally adopts a non-grounding or arc suppression coil grounding mode, and the single-phase grounding of the distribution network is represented as a low-current grounding fault mode. At present, the low-current ground fault detection technology still generally adopts a manual circuit pulling mode, so that time and labor are wasted, and unnecessary power failure loss is caused. According to statistics, about 20% of distribution network faults are caused by manual switch pulling due to low-current grounding, and the distribution network reliability is greatly influenced. Meanwhile, along with the improvement of the lean degree of distribution network operation and inspection, the fault section needs to be quickly positioned, and more seriously, along with the wide access of a distributed power supply in a distribution network, the requirement on the efficient fault positioning of the distribution network is higher and higher. The small-current ground fault positioning technology is influenced by factors such as weak fault signals, complex field operation environment, low reliability of fault detection equipment, various fault reasons and the like, and the fault detection accuracy is low, so that the small-current ground fault positioning technology needs to be solved urgently.
Disclosure of Invention
The invention aims to solve the technical problems that the small-current ground fault positioning technology in the prior art is influenced by single signal source information loss and weak information source, and the fault detection accuracy and reliability are low, and provides a high-precision small-current ground fault positioning technology.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
in one aspect, the present invention provides a single-phase ground fault location method, including:
collecting fault data collected by each detection device;
preprocessing fault data, wherein the fault data comprise zero sequence voltage, and when the zero sequence voltage measured by any one detection device exceeds a preset threshold value, determining that a small current ground fault occurs;
after the small current ground fault is determined to occur, the fault information integrity of each detection device is calculated, and the confidence coefficient ri of the fault studying and judging result is assigned according to the information integrity;
when the fault information is complete, judging that the confidence coefficient of the fault study result of the selected detection device meets a specific requirement, and judging the single-phase earth fault section by using each fault detection device to obtain the fault section identification result of each fault detection device;
judging whether the identification results of the fault sections of the fault detection devices are consistent, and if so, determining that the identification results of the fault sections of the fault detection devices are the final fault sections;
and if the fault information of each fault detection device is incomplete or the confidence coefficient of the fault research and judgment result does not meet the specific requirement or the identification results of the fault sections are inconsistent, determining the final fault section by using a correlation coefficient method.
Preferably, the fault data further includes three-phase voltage information, three-phase current information, and zero-sequence current information.
In the above technical solution, the detection device includes a distribution automation management system, a power grid dispatching automation system, a power consumption information acquisition system, a fault indicator, and a low-current ground fault line selection device.
Further, the method for preprocessing the fault data comprises the following steps:
correcting the polarities of a PT (Phase voltage Transformers) and a CT (Current Transformer) by using the voltage and the Current under normal conditions, and determining whether a condition of reverse connection of the polarities exists;
analyzing and comparing voltage and current information collected by the small-current ground fault line selection device and the fault indicator to determine the fault occurrence time;
respectively calculating the mutation quantity of the voltage and the current collected by the low-current ground fault line selection device and the fault indicator, and when the mutation quantity of 3 points continuously reaches a setting threshold, judging that the previous point of the first mutation quantity exceeding the point corresponding to the setting threshold is a fault starting moment;
after the fault occurrence time is determined, processing fault data by using FFT (fast Fourier transform) conversion, and calculating the amplitude and the phase of the steady-state current;
and carrying out interpolation processing on the transient zero-sequence current of the small-current ground fault line selection device or the fault indicator to ensure that the frequencies are the same.
In the above technical solution, the calculation formula of the integrity of the fault information of each detection device is as follows:
When the fault information is complete lambdaiDetermining that the fault information of the fault detection device is complete when the integrity setting threshold is greater than or equal to; otherwise the integrity of the fault information is lambdaiAnd when the integrity setting threshold is smaller than the integrity setting threshold, judging that the fault information of the fault detection device is incomplete, wherein the value of the integrity setting threshold is 0.7.
In the above technical solution, the method for determining the fault section by using the correlation coefficient method is as follows:
if the waveform similarity coefficient of the transient zero-sequence current measured by the detection devices of the detection points at the two ends of the section does not reach a similar threshold value, the section is a non-fault section;
when the waveform similarity coefficient of the transient zero-sequence current measured by the detection devices of the detection points at the two ends reaches a similar threshold value, determining a fault section;
the expression of the similarity coefficient is as follows:
where ρ isi(i+1)Similarity coefficients of transient zero sequence current waveforms of the ith set of fault detection device and the (i + 1) th set of fault detection device are obtained; i.e. i0i(xj) For transient zero sequence currents of the ith fault detection unit0(i+1)(xj) The transient zero sequence current of the (i + 1) th fault detection device.
In another aspect, the present invention provides a single-phase ground fault location method system, including: the system comprises a big data analysis platform and a plurality of fault detection devices;
the plurality of fault detection devices are used for collecting fault data;
the big data analysis platform is used for collecting fault data collected by each detection device;
the big data analysis platform is also used for preprocessing fault data, the fault data comprise zero sequence voltage, and when the zero sequence voltage measured by any detection device exceeds a preset threshold value, a small current ground fault is determined to occur; after the small current ground fault occurs, the big data analysis platform calculates the fault information integrity of each detection device, and assigns a value to the confidence coefficient ri of the fault study and judgment result according to the information integrity;
when the fault information of each detection device is complete, judging that the confidence coefficient of the fault research and judgment result of the selected detection device meets a specific requirement, judging the single-phase earth fault section by using each fault detection device to obtain the fault section identification result of each fault detection device;
judging whether the identification results of the fault sections of the fault detection devices are consistent, and if so, determining that the identification results of the fault sections of the fault detection devices are the final fault sections;
and if the fault information of each fault detection device is incomplete or the confidence coefficient of the fault research and judgment result does not meet the specific requirement or the identification results of the fault sections are inconsistent, determining the final fault section by using a correlation coefficient method.
The invention achieves the following beneficial effects:
1. the fault detection equipment in the distribution network is utilized to the maximum extent, the small-current grounding fault positioning technology based on multi-source information is realized, and the defect of low precision of the existing fault positioning technology based on single-source information is overcome;
2. the invention provides a small-current grounding fault positioning technology based on multi-source information, which can overcome the defects of long power failure time and large maintenance amount of the existing manual pulling and manual line patrol.
3. Due to the fact that field operation conditions are severe, the conditions that the polarity of the sensor is reversely connected, a fault indicator is not started, the fault indicator is disconnected and the like are incomplete exist; in order to ensure the correctness of the judgment of the fault section and improve the accuracy and the reliability of the method, the invention adopts a data preprocessing step, which comprises the steps of correcting the polarity of voltage and current, judging the integrity of data and realizing the consistency of the frequency of each detection device through interpolation processing.
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FIG. 1 is a flow chart of a method of an embodiment of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
After a low-current ground fault occurs, the following characteristics exist:
1) the fault phase voltage is reduced, the non-fault phase voltage is increased, and the neutral point voltage is shifted;
2) the transient zero-sequence current amplitude of the fault line is larger than that of the non-fault line, and the polarities are opposite;
3) transient zero-sequence current amplitudes at two ends of the fault section are large, polarities are opposite, and transient waveforms are dissimilar; transient zero-sequence current amplitudes at two ends of the non-fault section are close, the polarities are the same, and the waveforms are similar;
4) for a neutral point ungrounded system, the steady-state zero-sequence current of a fault line is larger than that of a non-fault line, and the polarities are opposite;
5) for a neutral point ungrounded system, the steady-state current amplitudes at the two ends of the fault section are larger and have opposite polarities, and the current amplitudes at the two ends of the non-fault section are close and have the same polarity;
6) for a system with a neutral point grounded through an arc suppression coil, no obvious fault characteristic exists in the steady-state zero-sequence current of a fault line;
7) for a system with a neutral point grounded through an arc suppression coil, no obvious fault characteristics exist in the steady-state zero-sequence currents at two ends of a fault section.
The detection platform and the system developed in the prior art are provided with a D5000 system, a PMS2.0 system, a distribution network automation system, an electricity utilization information acquisition system, a fault statistics reporting system and meteorological system data fusion, so that the complete process of distribution accounts, distribution transformation operation data and meteorological data of substation outlet switch tripping, switch operation data, switch equipment accounts, distribution network lines, distribution transformers and the like is communicated, a power grid transformation tripping database is constructed, splicing of the equipment accounts, the operation data and the meteorological data is realized, and data cleaning and fusion of multi-field and multi-service scenes are realized.
The small-current grounding fault positioning technology is influenced by factors such as weak fault signals, complex field operation environment, low reliability of fault detection equipment, various fault reasons and the like, the fault detection accuracy is low, and the fault detection is always a worldwide problem.
Example 1: FIG. 1 is a flow chart of a method of an embodiment of the present invention. Fig. 1 shows a single-phase earth fault location method, comprising:
(1) collecting fault data collected by each detection device;
(2) preprocessing fault data, wherein the fault data comprise zero sequence voltage, and when the zero sequence voltage measured by any one detection device exceeds a preset threshold value, determining that a small current ground fault occurs;
(3) after the small current ground fault is determined to occur, the fault information integrity of each detection device is calculated, and the confidence coefficient ri of the fault studying and judging result is assigned according to the information integrity;
(4) when the fault information is complete, judging that the confidence coefficient of the fault study result of the selected detection device meets a specific requirement, and judging the single-phase earth fault section by using each fault detection device to obtain the fault section identification result of each fault detection device;
(5) judging whether the identification results of the fault sections of the fault detection devices are consistent, and if so, determining that the identification results of the fault sections of the fault detection devices are the final fault sections;
(6) if the fault information of each fault detection device is incomplete or the confidence coefficient of the fault study result does not meet the specific requirement or the identification results of the fault sections are inconsistent, the acquired information is utilized to carry out correlation (namely, correlation coefficient method) operation, and finally the fault sections are determined. Preferably, after the fault section is judged, the fault is also judged, and if the fault is a transient fault, the fault is recorded; if the fault is a permanent fault, alarming and recording the fault.
The high-precision low-current grounding fault locating technology based on multi-source information fusion overcomes the defects of information loss and weak information source of a single signal source, can achieve supporting fault data processing (confidence, redundancy and the like) and fault data fusion, and further achieves high-precision fault locating.
On the basis of the above embodiment, further, in other embodiments, when the fault information of each fault detection device is incomplete, the finally determined fault section is corrected in combination with the historical fault information. The historical database is a database of a big data analysis platform, and when an information source is lost or data is unreliable, various historical information can be used for deducing a fault positioning section.
Example 2: on the basis of the above embodiments, the present embodiment comprehensively utilizes information acquired by systems such as a distribution automation master station, a novel distribution terminal, fault indication, and the like, and based on a big data analysis platform, starts from a low-current ground fault characteristic, and combines action characteristics of an existing distribution automation system, a scheduling automation system, a fault indicator, and a low-current ground fault line selection device to realize high-precision and high-accuracy fault location.
Each detection device as a data source of multi-source information in the present embodiment includes:
1) distribution automation management system
Distribution network automation management system is an information integration and comprehensive utilization system, and this patent utilizes the information of distribution automation main website system as follows:
the alarm information of 3U0 assists in judging whether single-phase earth fault occurs, and if the alarm information of 3U0 exists, single-phase earth fault may occur;
monitoring a power failure area by utilizing real-time monitoring voltage and current data so as to confirm a single-phase earth fault positioning result detected based on a big data analysis platform, and storing fault position information into a historical fault information base after determining that fault information really occurs;
2) power grid dispatching automation system
The power failure range is monitored by voltage and current information acquired by a power grid dispatching automation system in real time, so that the single-phase earth fault positioning result of the big data analysis platform is confirmed, and after the fault is determined to be actually generated, fault position information is stored in a historical fault information base.
3) Electricity consumption information acquisition system
The data that the power consumption information acquisition system gathered include: and voltage and current information are used for determining the power failure range and the power failure time. And the big data analysis platform determines the accuracy of the fault positioning result by using the data and combining the fault positioning result.
And (3) calculating the accuracy of the fault positioning result:
wherein
The number of fault lines calculated by a fault positioning algorithm based on multi-source information fusion is calculated;
the number of lines of the actual fault power failure after the system is confirmed is used.
The accuracy information of the positioning result is utilized, firstly, the positioning result of the big data analysis platform is fed back, so that the improvement of the positioning algorithm of the big data analysis platform is realized; secondly, determining a fault high-power-generation range by combining the power failure range and the fault judgment range, and guiding the optimal installation position of the fault indicator; thirdly, the fault positioning result and the fault positioning accuracy are combined to determine the optimal power supply mode.
4) Fault indicator
The fault indicator is a device installed on a power line (overhead line, cable, and bus bar) to indicate a fault current. Most fault indicators can discriminate, indicate a short circuit fault by detecting the characteristics of the short circuit current.
In this embodiment, a transient logging-type fault indicator is preferably used. The transient recording type fault indicator comprehensively utilizes an intelligent sensor technology, a signal processing technology, an artificial intelligence technology and an information communication technology, high-precision real-time on-line monitoring of medium-voltage distribution network line current and a ground electric field is realized, high-sampling recording is triggered when the state of a line is abnormally changed, accurate positioning of a small-current grounding system ground fault, backtracking and inversion of a complex fault process and early warning of an abnormal state of the line can be realized according to recording data, the line fault recovery time is effectively shortened, passive repair reporting is changed into active monitoring, the operation and maintenance level of the distribution network is practically improved, and the benefit is improved.
The data it collects include: three-phase voltage, current, zero-sequence voltage, zero-sequence current information. The big data analysis platform utilizes three-phase voltage and current information of the transient recording type fault indicator and calculates a zero-sequence component, wherein the voltage and current calculation method comprises the following steps:
U0＝(UA+UB+UC)/3
I0＝(IA+IB+IC)/3
and (3) judging the disconnection of the three-phase voltage and three-phase current information acquired by the transient recording type fault indicator, and judging that the disconnection fault occurs when the voltage exists on the line and the current does not exist.
And (4) performing correlation coefficient operation on zero sequence current information calculated by two adjacent sets of transient recording type fault indicators by using a big data analysis platform, and judging the fault section when the correlation coefficient is smaller.
5) Small current grounding fault line selection device
The data it collects include: zero sequence voltage, zero sequence current information and a line selection result.
The large data analysis platform collects zero sequence voltage and zero sequence current information collected by the small current ground fault line selection device and line selection results of the small current ground fault line selection device.
And judging a fault outgoing line by using a small current ground fault line selection result, and then performing related system calculation by using zero sequence current information acquired by a transient recording type fault indicator on the fault outgoing line so as to realize the judgment of a fault section. And the zero sequence current information of the fault feeder outlet acquired by the low-current ground fault line selection device and the zero sequence current information acquired by the transient recording type fault indicator closest to the transformer substation are utilized to calculate the correlation coefficient, so that the fault judgment of the dead zone can be realized.
The single-phase earth fault positioning method provided by the embodiment comprises the following steps:
(1) collecting fault data collected by each detection device, wherein the detection devices comprise a power distribution automatic management system, a power grid dispatching automatic system, a power utilization information collection system, a fault indicator and a low-current grounding fault line selection device; because the existing fault indicator mostly relies on field electric field change to start detection, and the probability that the fault indicator is not started is higher, the fault detection command is sent to the fault indicator by the big data analysis platform, and the fault information collected by the fault indicator is sent to the big data analysis platform.
(2) Fault data is preprocessed, wherein the fault data comprises zero sequence voltage. In this embodiment, the low-current ground fault line selection device or the fault indicator in the substation detects zero-sequence voltage, and when the zero-sequence voltage detected by any one of the detection devices exceeds a predetermined threshold value, it is determined that a low-current ground fault occurs and fault information is sent to the big data analysis platform.
(3) And after the small current ground fault is determined to occur, the fault information integrity of each detection device is calculated, and the confidence coefficient ri of the fault studying and judging result is assigned according to the information integrity. When the information integrity is low, the confidence coefficient is low, namely the result is not credible; preferably, the confidence score is assigned using an analytic hierarchy process.
The method comprises the steps that a big data analysis platform is used for collecting uploading information of all systems (a power distribution automation system, a dispatching automation system, a transient recording type fault indicator and a low-current ground fault line selection device) to confirm whether a low-current ground fault occurs or not, and after the fact that the low-current ground fault occurs is confirmed, the big data analysis platform confirms the integrity of the uploading data of all the systems to confirm whether data are lost or not.
(4) When the fault information is complete, judging that the confidence coefficient of the fault study result of the selected detection device meets a specific requirement, and judging the single-phase earth fault section by using each fault detection device to obtain the fault section identification result of each fault detection device; in this embodiment, the confidence levels of the fault studying and judging results of all the detecting devices are ranked from high to low, and when the confidence levels of the fault studying and judging results of the small-current ground fault line selecting device and the transient recording type fault indicator are ranked in the first two digits, the confidence level of the fault studying and judging result of the selected detecting device meets the specific requirement. Each detection device adopts the prior art to determine the single-phase earth fault section, which is not described herein.
(5) Judging whether the identification results of the fault sections of the fault detection devices are consistent, and if so, determining that the identification results of the fault sections of the fault detection devices are the final fault sections;
(6) if the fault information of each fault detection device is incomplete or the confidence coefficient of the fault study result does not meet specific requirements or the identification results of the fault sections are inconsistent, determining the final fault section by using a correlation coefficient method, and alarming and recording the fault;
on the basis of the above embodiments, in order to ensure the correctness of the fault section discrimination and improve the accuracy and reliability of the method of the present invention, the data preprocessing step adopted in the specific embodiment includes the steps of correcting the polarities of the voltage and the current, judging the integrity of the data, and realizing the frequency consistency of each detection device through interpolation processing.
Preferably, the method for preprocessing the fault data is as follows:
correcting the polarities of PT and CT by using the voltage and current under normal condition, and determining whether the condition of polarity reversal exists;
analyzing and comparing voltage and current information collected by the small-current ground fault line selection device and the transient recording type fault indicator to determine the fault occurrence time;
respectively calculating the mutation quantity of the voltage and the current collected by the low-current ground fault line selection device and the fault indicator, and when the mutation quantity of 3 points continuously reaches a setting threshold, judging that the previous point of the first mutation quantity exceeding the point corresponding to the setting threshold is a fault starting moment;
after the fault occurrence time is determined, processing fault data by using Fast Fourier Transform (FFT) to calculate the amplitude and phase of the steady-state current; the FFT is a fast algorithm of Discrete Fourier Transform (DFT), i.e. FFT, which is the prior art and is not described herein.
And (3) carrying out interpolation processing on the transient zero-sequence current of the small-current ground fault line selection device or the transient recording type fault indicator to ensure that the frequencies are the same.
Preferably, the polarity of PT and CT is corrected by the voltage and current in the normal case, and the method of determining whether there is a reverse polarity condition is as follows:
calculating an included angle theta between a voltage U and a current I by utilizing voltage and current information acquired by PT and CT under a normal condition:
θ＝arg(U/I)
if the tail end of the line is an electric load, when the voltage leads the current, namely theta is larger than 0 degree, the PT and CT are correctly wired;
when the voltage lags the current, namely theta is less than 0 degrees, the polarity of the CT is judged to be reversely connected;
if the tail end of the circuit is a power supply, when the voltage lags the current, namely theta is less than 0 DEG, the PT and the CT are correctly wired; when the voltage leads the current, namely theta is larger than 0 DEG, the polarity of the CT is determined to be reversely connected.
The fault information integrity calculation formula of each detection device is as follows:
when the fault information is complete lambdaiDetermining that the fault information of the fault detection device is complete when the integrity setting threshold is greater than or equal to; otherwise the integrity of the fault information is lambdaiAnd when the integrity setting threshold is smaller than the integrity setting threshold, judging that the fault information of the fault detection device is incomplete, and preferably, the value of the integrity setting threshold is 0.7.
In the specific embodiment, preferably, the method for determining the fault section by using the correlation coefficient method in the specific embodiment is as follows: if the waveform similarity coefficient of the transient zero-sequence current measured by the detection devices of the detection points at the two ends of the section does not reach a similar threshold value, the section is a non-fault section;
when the waveform similarity coefficient of the transient zero-sequence current measured by the detection devices of the detection points at the two ends reaches a similar threshold value, determining a fault section;
the expression of the similarity coefficient is as follows:
where ρ isi(i+1)Similarity coefficients of transient zero sequence current waveforms of the ith set of fault detection device and the (i + 1) th set of fault detection device are obtained; i.e. i0i(xj) For transient zero sequence currents of the ith fault detection unit0(i+1)(xj) The transient zero sequence current of the (i + 1) th fault detection device.
Another embodiment provides a single-phase ground fault location method system, including: the system comprises a big data analysis platform and a plurality of detection devices;
the plurality of fault detection devices are used for collecting fault data;
the big data analysis platform is used for collecting fault data collected by each detection device;
the big data analysis platform is also used for preprocessing fault data, the fault data comprise zero sequence voltage, and when the zero sequence voltage measured by any detection device exceeds a preset threshold value, a small current ground fault is determined to occur; after the small current ground fault occurs, the big data analysis platform calculates the fault information integrity of each detection device, and assigns a value to the confidence coefficient ri of the fault study and judgment result according to the information integrity;
when the fault information is complete, judging that the confidence coefficient of the fault study result of the selected detection device meets a specific requirement, and judging the single-phase earth fault section by using each fault detection device to obtain the fault section identification result of each fault detection device;
judging whether the identification results of the fault sections of the fault detection devices are consistent, and if so, determining that the identification results of the fault sections of the fault detection devices are the final fault sections;
and if the fault information of each fault detection device is incomplete or the confidence coefficient of the fault research and judgment result does not meet the specific requirement or the identification results of the fault sections are inconsistent, determining the final fault section by using a correlation coefficient method.
The fault data collected by the detection devices are collected, fusion of multi-source data is achieved, fault detection equipment in a distribution network is utilized to the maximum extent, a small-current grounding fault positioning technology based on multi-source information is achieved, and the defect that the existing fault positioning technology based on single-source information is low in precision is overcome.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A single-phase earth fault positioning method is characterized by comprising the following steps: collecting fault data collected by each detection device; preprocessing fault data; the fault data comprises zero sequence voltage, and when the zero sequence voltage measured by any one detection device exceeds a preset threshold value, the occurrence of the small current ground fault is determined;
calculating the fault information integrity of each detection device after the small current ground fault occurs, and assigning a value to the fault study and judgment result confidence ri of each detection device according to the information integrity; when the fault information of each detection device is complete, judging that the confidence coefficient of the fault research and judgment result of the selected detection device meets a specific requirement, judging the single-phase earth fault section by using each fault detection device to obtain the fault section identification result of each fault detection device; judging whether the identification results of the fault sections of the fault detection devices are consistent, and if so, determining that the identification results of the fault sections of the fault detection devices are the final fault sections; if the fault information of each fault detection device is incomplete or the confidence coefficient of the fault study result does not meet the specific requirement or the identification results of the fault sections are inconsistent, determining the final fault section by using a correlation coefficient method; the pretreatment comprises the following steps: correcting the polarities of PT and CT by using the voltage and current under normal condition, and determining whether the condition of polarity reversal exists; analyzing and comparing voltage and current information collected by the small-current ground fault line selection device and the fault indicator to determine the fault occurrence time;
respectively calculating the mutation quantity of the voltage and the current collected by the low-current ground fault line selection device and the fault indicator, and when the mutation quantity of 3 points continuously reaches a setting threshold, judging that the previous point of the first mutation quantity exceeding the point corresponding to the setting threshold is a fault starting moment;
after the fault occurrence time is determined, processing fault data by using FFT (fast Fourier transform) conversion, and calculating the amplitude and the phase of the steady-state current;
and carrying out interpolation processing on the transient zero-sequence current of the small-current ground fault line selection device or the fault indicator to ensure that the frequencies are the same.
2. The single-phase ground fault location method of claim 1, wherein the fault data further comprises three-phase voltage information, three-phase current information, and zero-sequence current information.
3. The single-phase ground fault location method of claim 1,
the detection device comprises a power distribution automatic management system, a power grid dispatching automatic system, a power utilization information acquisition system, a fault indicator and a low-current grounding fault line selection device.
4. The single-phase earth fault location method of claim 1, wherein the polarity of PT and CT is corrected using the normal voltage and current, and the method of determining whether there is a polarity reversal is as follows:
calculating an included angle theta between a voltage U and a current I by using voltage and current information acquired by PT and CT under a normal condition, wherein the expression is as follows:
θ＝arg(U/I)
if the tail end of the line is an electric load, when the voltage leads the current, namely theta is larger than 0 degree, the PT and CT are correctly wired;
when the voltage lags the current, namely theta is less than 0 degrees, the polarity of the CT is judged to be reversely connected;
if the tail end of the circuit is a power supply, when the voltage lags the current, namely theta is less than 0 DEG, the PT and the CT are correctly wired; when the voltage leads the current, namely theta is larger than 0 DEG, the polarity of the CT is determined to be reversely connected.
5. The single-phase ground fault location method of claim 1,
and detecting the zero sequence voltage by adopting a fault indicator or a small current ground fault line selection device in the transformer substation.
6. A single-phase earth fault location method according to claim 1, characterized in that the fault information integrity λ of each detection meansiThe calculation formula is as follows:
7. The single-phase earth fault location method of claim 6, wherein λ is a fault information integrityiDetermining that the fault information of the fault detection device is complete when greater than or equal to an integrity setting thresholdOf (1); otherwise the integrity of the fault information is lambdaiAnd when the integrity setting threshold is smaller than the integrity setting threshold, judging that the fault information of the fault detection device is incomplete, wherein the value of the integrity setting threshold is 0.7.
8. The single-phase ground fault location method of claim 1,
the method for determining the fault section by using the correlation coefficient method comprises the following steps:
if the waveform similarity coefficient of the transient zero-sequence current measured by the detection devices of the detection points at the two ends of the section does not reach a similar threshold value, the section is a non-fault section;
when the waveform similarity coefficient of the transient zero-sequence current measured by the detection devices of the detection points at the two ends reaches a similar threshold value, determining a fault section;
the expression of the similarity coefficient is as follows:
where ρ isi(i+1)Similarity coefficients of transient zero sequence current waveforms of the ith set of fault detection device and the (i + 1) th set of fault detection device are obtained; i.e. i0i(xj) For transient zero sequence currents of the ith fault detection unit0(i+1)(xj) The transient zero sequence current of the (i + 1) th fault detection device.
9. The single-phase earth fault positioning method system is characterized by comprising the following steps: the system comprises a big data analysis platform and a plurality of fault detection devices;
the plurality of fault detection devices are used for collecting fault data;
the big data analysis platform is used for collecting fault data collected by each detection device;
the big data analysis platform is also used for preprocessing fault data, the fault data comprise zero sequence voltage, and when the zero sequence voltage measured by any detection device exceeds a preset threshold value, a small current ground fault is determined to occur; after the small current ground fault occurs, the big data analysis platform calculates the fault information integrity of each detection device, and assigns a value to the confidence coefficient ri of the fault study and judgment result according to the information integrity;
when the fault information of each detection device is complete, judging that the confidence coefficient of the fault research and judgment result of the selected detection device meets a specific requirement, judging the single-phase earth fault section by using each fault detection device to obtain the fault section identification result of each fault detection device; judging whether the identification results of the fault sections of the fault detection devices are consistent, and if so, determining that the identification results of the fault sections of the fault detection devices are the final fault sections; if the fault information of each fault detection device is incomplete or the confidence coefficient of the fault study result does not meet the specific requirement or the identification results of the fault sections are inconsistent, determining the final fault section by using a correlation coefficient method;
the pretreatment comprises the following steps: correcting the polarities of PT and CT by using the voltage and current under normal condition, and determining whether the condition of polarity reversal exists; analyzing and comparing voltage and current information collected by the small-current ground fault line selection device and the fault indicator to determine the fault occurrence time;
respectively calculating the mutation quantity of the voltage and the current collected by the low-current ground fault line selection device and the fault indicator, and when the mutation quantity of 3 points continuously reaches a setting threshold, judging that the previous point of the first mutation quantity exceeding the point corresponding to the setting threshold is a fault starting moment;
after the fault occurrence time is determined, processing fault data by using FFT (fast Fourier transform) conversion, and calculating the amplitude and the phase of the steady-state current;
and carrying out interpolation processing on the transient zero-sequence current of the small-current ground fault line selection device or the fault indicator to ensure that the frequencies are the same.
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| CN110850333B (en) * | 2019-11-20 | 2021-11-05 | 吉林松江河水力发电有限责任公司 | Phase identification method for single-phase earth fault of low-voltage distribution system |
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| CN112415326B (en) * | 2020-10-22 | 2022-02-11 | 中国矿业大学 | Power distribution network fault section identification method based on fuzzy clustering algorithm |
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| CN113311288B (en) * | 2021-05-11 | 2022-09-27 | 国网浙江省电力有限公司湖州供电公司 | Small current grounding fault searching and positioning method and system |
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| CN114355111A (en) * | 2022-03-21 | 2022-04-15 | 智联新能电力科技有限公司 | Power distribution network fault positioning method based on improved incidence matrix |
| CN115575765B (en) * | 2022-10-31 | 2023-06-30 | 国网浙江省电力有限公司金华供电公司 | Ground fault section selection analysis system based on distribution automation four-region data |
| CN116359668A (en) * | 2023-03-15 | 2023-06-30 | 国网宁夏电力有限公司银川供电公司 | Power distribution network single-phase earth fault positioning method based on multi-source information comprehensive judgment |
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