CN113311288B - Small current grounding fault searching and positioning method and system - Google Patents
Small current grounding fault searching and positioning method and system Download PDFInfo
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- CN113311288B CN113311288B CN202110511190.3A CN202110511190A CN113311288B CN 113311288 B CN113311288 B CN 113311288B CN 202110511190 A CN202110511190 A CN 202110511190A CN 113311288 B CN113311288 B CN 113311288B
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
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Abstract
The invention discloses a method and a system for searching and positioning a low-current ground fault, which comprise the following steps: detecting the three-phase voltage change by the fault monitoring device, and calling and testing and storing load data; extracting historical load data meeting the requirement of load data confidence; calculating zero sequence break currents of all fault monitoring devices, and marking the fault monitoring devices with the zero sequence break currents exceeding a threshold value; and judging the fault line and the fault section according to the marked fault monitoring device. According to the method, line selection and fault section positioning of the low-current ground fault line are realized through changes of zero-sequence voltage and current amplitude values and phase fault characteristic changes before and after faults and installation positions of fault monitoring devices in the distribution network topological structure, historical data of inaccurate fault monitoring devices are preprocessed, inaccurate data secondary processing is carried out according to the distribution network topological structure after the zero-sequence current abrupt change value is calculated, the ground fault section can be accurately searched, and power supply reliability is improved.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a small-current ground fault searching and positioning method and system.
Background
After permanent single-phase grounding occurs in a low-current grounding system, a short circuit loop is not formed, grounding current is low, a fault signal is weak, and therefore positioning of a grounding fault section is difficult. The fault indicator in the existing distribution automation system has no function of positioning a low-current grounding fault interval, and the fault position is still determined by widely adopting a manual line patrol method on site. The distribution network line branch is many, the distance is far away, and it is very difficult that manual inspection line location fault location. And the faults are mostly invisible faults, the fault point is very inconvenient to find, a large amount of manpower and material resources are consumed, and the short-time power failure caused by the open circuit still causes great economic loss for users. The fault studying and judging function of the fault monitoring device in the distribution automation system is generally used for line short-circuit faults. Because the short-circuit current can reach several times to dozens of times of the load current, the short-circuit current is easily distinguished from the load current. However, when the line is grounded in a single phase, the grounding current is only increased by a few amperes to dozens of amperes, meanwhile, because the zero sequence current transformer of the fault monitoring device is generally low in precision, and because the problems of product quality, installation and maintenance and the like easily cause misjudgment of a grounding fault interval, the robustness is poor, and because the fault monitoring device is exposed to wind, rain and rain outdoors and the product quality is caused, a part of fault monitoring devices collect load data which are missed in collection and mistransmission, and the data quality has certain influence on ground fault research and judgment. Therefore, when the fault characteristic current is not obvious enough, the fault monitoring device cannot automatically judge and distinguish the fault characteristic current from the load current under the common condition.
For example, chinese patent CN111650474A, published 2020, 9, 11, discloses a method for locating an interphase short-circuit fault section of a power distribution network based on multi-system fusion, which uses a distribution automation system as a core, a GIS system, a PMS system, an EMS system, and an electricity consumption information acquisition system as fault data sources, fuses internal data of each system according to a certain standard, and analyzes and processes the data to locate an interphase short-circuit fault section of the power distribution network, including identifying a fault line, determining a distribution transformer number and a line segment where a transformer is located, determining information of the distribution transformer, collecting information of the distribution transformer in the fault line, and determining a fault section. The method can be used for quickly positioning the section of the short-circuit fault of the power distribution network, but the section of the fault cannot be accurately determined for the small-current grounding fault such as single-phase grounding of the line.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the technical problem that the existing power distribution network line fault section positioning method cannot accurately position the fault section of the single-phase earth fault is solved. A small-current ground fault searching and positioning method and system capable of rapidly determining a single-phase ground fault section are provided.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a small current ground fault searching and positioning method comprises the following steps:
s1: detecting the three-phase voltage change by the fault monitoring device, and calling and testing and storing load data;
s2: extracting historical load data meeting the requirement of load data confidence;
s3: calculating zero sequence break currents of all fault monitoring devices, and marking the fault monitoring devices with the zero sequence break currents exceeding a threshold value;
s4: and judging the fault line and the fault section according to the marked fault monitoring device. By means of multi-source ground fault characteristic information fusion judgment, namely through zero-sequence voltage before and after a fault, current amplitude change and phase fault characteristic change and the installation position of a fault monitoring device in a distribution network topological structure, line selection and fault section positioning of a low-current ground fault line are achieved, and therefore power supply of a non-fault section is recovered quickly. And for the error historical data of the fault monitoring device, the historical data of the inaccurate fault monitoring device is preprocessed, after the zero-sequence current mutation value is calculated, the inaccurate data is secondarily processed according to the distribution network topological structure, and the robustness of the earth fault line and interval judgment is improved.
Preferably, the step S2 includes the following steps:
s21: reading historical load data of each fault monitoring device of the distribution line;
s22: judging whether the historical load data of each fault monitoring device meets the load data confidence requirement, if so, entering step S24, otherwise, entering step S23;
s23: ignoring fault monitoring devices that do not meet load data confidence requirements;
s24: and keeping and extracting historical load data of the fault monitoring device meeting the load data confidence requirement. And analyzing historical data of all distribution line fault monitoring devices under the transformer substation, judging that the confidence coefficient of the historical load data of the selected fault monitoring device meets a specific requirement, and keeping the selected fault monitoring device participating in fault positioning judgment.
Preferably, the process of determining the load data confidence requirement in step S22 includes the following steps:
a1: reading historical load data of a fault monitoring device;
a2: judging whether the historical ABC three-phase current balance degree in the historical load data is smaller than a set threshold value a, if so, entering the step A3, and if not, entering the step A6;
a3: judging whether the ratio of the zero-sequence current amplitude to the maximum phase current in the historical load data is smaller than a set threshold b, if so, entering a step A4, otherwise, entering a step A6;
a4: judging whether the ABC three-phase currents in the historical load data are all larger than a set threshold value c, if so, entering the step A5, and if not, entering the step A6;
a5: the historical load data of the fault monitoring device meets the requirement of load data confidence;
a6: historical load data of the fault monitoring device does not meet the load data confidence requirement;
a7: the historical load data of the next fault monitoring device is read and the process returns to step a 2. The historical load data of one fault monitoring device can be randomly read, and after the load data is judged according to the judgment condition required by the confidence degree of the load data, the historical load data of a new fault monitoring device which is not read is read. And the confidence of the historical load data result is that the ABC three-phase current is respectively greater than a set threshold value c according to the fact that the historical ABC three-phase current balance degree is less than a set threshold value a, the zero-sequence current amplitude/maximum phase current is less than a set threshold value b. Because the three-phase imbalance conditions of distribution networks with different structures and different loads are different, the setting threshold value a, the setting threshold value b and the setting threshold value c need to be adjusted adaptively according to the conditions of different distribution networks, and if the above 3 conditions are met, the confidence of the historical load data result of the fault monitoring device is met.
Preferably, the step S3 includes the following steps:
s31: extracting amplitude and phase data of zero sequence current of the fault monitoring device meeting confidence level requirements;
s32: calculating the zero sequence current amplitude variation before and when the fault of each fault monitoring device occurs;
s33: sequencing the fault monitoring devices according to the amplitude variation of the corresponding zero sequence current from large to small;
s34: setting a zero-sequence current mutation threshold value y;
s35: sequentially comparing the zero-sequence current amplitude variation of the fault monitoring device with a zero-sequence current mutation threshold value y according to the sequence;
s36: judging whether the zero sequence current amplitude variation of the fault monitoring device is larger than a zero sequence current mutation threshold value y, if so, entering a step S37, otherwise, entering a step S38;
s37: marking the fault monitoring devices for comparison, selecting the next fault monitoring device according to the sequence for comparison, and returning to the step S36;
s38: and recording and storing the marked fault monitoring device information. And extracting all fault monitoring device data with confidence degrees meeting the requirements to perform zero sequence current amplitude and phase comparison. And comparing the zero-sequence current amplitude and the phase before and when the fault occurs, and sequencing according to the zero-sequence current change amplitude from large to small. And if the zero sequence sudden change current of a certain fault monitoring device is larger than a threshold value, marking the fault monitoring device. Calculating the zero-sequence current amplitude variation before and when the fault occurs in each fault monitoring device, namely calculating the break current when the fault occurs in each fault monitoring device, sequencing the fault monitoring devices according to the corresponding zero-sequence current amplitude variation from large to small so as to be convenient for marking, wherein the zero-sequence current amplitude variation of the front fault monitoring device is larger than a break threshold value y when the fault monitoring devices are marked in sequence, and when the zero-sequence current amplitude variation of one fault monitoring device is detected to be smaller than the break threshold value y, the zero-sequence current amplitude variation of the rear fault monitoring device is smaller than the break threshold value y, so that the rear fault monitoring devices do not need to be searched and marked.
Preferably, the step S4 includes the following steps:
s41: counting distribution lines to which the marked fault monitoring devices belong;
s42: judging whether the distribution lines to which the fault monitoring devices belong are the same line, if so, entering step S46, otherwise, entering step S43;
s43: judging whether the sudden change zero sequence current of each marked fault monitoring device flowing to the bus from the grounding point along the line has connectivity, if so, entering step S44, otherwise, entering step S45;
s44: keeping the mark that the sudden change zero sequence current has a connectivity fault monitoring device, and returning to the step S41;
s45: and eliminating the mark that the sudden change zero sequence current does not have a connectivity fault monitoring device, and returning to the step S41.
S46: selecting the distribution line as a ground fault line;
s47: calculating the distance from each marked fault monitoring device to the transformer substation;
s48: and judging the rear-section distribution line of the marking fault monitoring device farthest from the transformer substation as a ground fault section. Under the normal operation condition of a small current grounding system, zero sequence current and voltage cannot change suddenly but fluctuate within a certain range. When a permanent single-phase earth fault occurs, the direction of the zero-sequence current of the earth line flows from the earth point to the bus along the line, the amplitude and the phase of the zero-sequence current and the voltage of the fault monitoring device between the bus of the transformer substation and the fault point of the line are mutated, and the zero-sequence current and the voltage in a non-fault area are not mutated. And judging whether the marked fault monitoring devices belong to the same distribution line. If the lines are not the same, judging according to distribution network topological structure logic, judging whether the sudden change zero sequence current of the fault monitoring device flowing from the grounding point to the bus along the lines has connectivity or not, removing marks from the inconsistent fault monitoring devices, and then judging the distribution lines to which the marked fault monitoring devices belong again until the distribution lines to which the fault monitoring devices belong judge whether the lines are the same or not; and if the marked fault monitoring devices are all the lines A, selecting the ground fault line A as the line A, judging that the rear section of the marked fault monitoring device farthest from the transformer substation is a ground fault section according to the distribution network topological structure, setting the position of the marked fault monitoring device farthest from the transformer substation in the distribution line as an edge node of the fault section, and judging the distribution line, which is positioned at the node and far away from the transformer substation, in the distribution line as the ground fault section.
Preferably, the step S1 includes the following steps:
s11: the fault monitoring device detects and calculates the variable quantity of each phase voltage of the distribution line;
s12: setting a preset value x of the variable quantity of each phase voltage of the distribution line;
s13: judging whether the variation of each phase voltage of the distribution line exceeds a preset value x, if so, performing step S14, otherwise, returning to step S11;
s14: and carrying out load data calling and storing on the fault monitoring devices of all distribution lines under the transformer substation. When the distribution line has a single-phase earth fault, the fault monitoring device detects that three-phase voltage changes, such as one-phase voltage rise and two-phase voltage drop, and the change amount exceeds a set threshold value, and load data is automatically called and tested and stored for the fault monitoring devices of all the distribution lines under the transformer substation.
The utility model provides a undercurrent earth fault seeks positioning system, utilizes above-mentioned method, includes the fault information collection module, the fault information collection module is with data transmission for fault area orientation module, the fault information collection module is including the detecting element who is used for detecting distribution lines three-phase voltage change condition and the data collection transmission unit who is used for with data transmission for fault area orientation module, fault area orientation module includes confidence coefficient analysis unit, zero sequence abrupt change current analysis unit and fault section judgement unit, confidence coefficient analysis unit in proper order with zero sequence abrupt change current analysis unit with fault section judgement unit connects, data collection transmission unit respectively with the detecting element with confidence coefficient analysis unit connects. A small current grounding fault finding and positioning system automatically detects three-phase voltage change through a fault information collection module and carries out fault monitoring device load data recall and storage on all distribution lines under a transformer substation, historical data confidence judgment and zero sequence current change amplitude judgment are sequentially carried out on collected fault monitoring device load data through a confidence coefficient analysis unit and a zero sequence current mutation analysis unit in a fault area positioning module, preprocessing of historical data is completed, a fault section is locked through a fault section judgment unit, and when the fault section cannot be locked, inaccurate data can be secondarily processed according to a distribution network topological structure so that the fault line and the fault section can be determined.
Preferably, the fault information collection module comprises a plurality of fault monitoring devices located on the distribution line. This patent is based on present fault monitoring device function, and the inaccurate fault monitoring device's of preliminary treatment data is judged through multisource earth fault characteristic information fusion to and the mounted position of fault monitoring device in joining in marriage net topology, realize undercurrent earth fault circuit route selection and trouble section location, solve the defect of the unable earth fault locate function of fault monitoring device.
The substantial effects of the invention are as follows: according to the invention, line selection and fault section positioning of a low-current ground fault line are realized through changes of zero-sequence voltage and current amplitude values and phase fault characteristic changes before and after a fault and installation positions of fault monitoring devices in a distribution network topological structure, historical data of inaccurate fault monitoring devices are preprocessed, and inaccurate data secondary processing is carried out according to the distribution network topological structure after a zero-sequence current abrupt change value is calculated.
Drawings
FIG. 1 is a flow chart of the main steps of the present embodiment;
FIG. 2 is a flowchart of step S22 according to the present embodiment;
FIG. 3 is a flowchart of step S3 according to the present embodiment;
fig. 4 is a schematic composition diagram of the present embodiment.
Wherein: 1. the system comprises a fault information collection module 2, a fault region positioning module 3, a detection unit 4, a data collection and transmission unit 5, a confidence coefficient analysis unit 6, a zero sequence abrupt change current analysis unit 7 and a fault section judgment unit.
Detailed Description
The following provides a more detailed description of the present invention, with reference to the accompanying drawings.
A small current ground fault locating method, as shown in fig. 1, includes the following steps:
s1: detecting the three-phase voltage change by the fault monitoring device, and calling and testing and storing load data; step S1 includes the following steps:
s11: detecting and calculating the variable quantity of each phase voltage of the distribution line by a fault monitoring device;
s12: setting a preset value x of the variable quantity of each phase voltage of the distribution line;
s13: judging whether the variation of each phase voltage of the distribution line exceeds a preset value x, if so, performing step S14, otherwise, returning to step S11;
s14: and carrying out load data calling and storing on the fault monitoring devices of all distribution lines under the transformer substation. When the distribution line has a single-phase earth fault, the fault monitoring device detects that three-phase voltage changes, such as one-phase voltage rise and two-phase voltage drop, and the change amount exceeds a set threshold value, and load data is automatically called and tested and stored for the fault monitoring devices of all the distribution lines under the transformer substation.
S2: extracting historical load data meeting the requirement of load data confidence; step S2 includes the following steps:
s21: reading historical load data of each fault monitoring device of the distribution line;
s22: judging whether the historical load data of each fault monitoring device meets the load data confidence requirement, if so, entering step S24, otherwise, entering step S23;
s23: ignoring fault monitoring devices that do not meet load data confidence requirements;
s24: and keeping and extracting historical load data of the fault monitoring device meeting the load data confidence requirement. And analyzing historical data of all distribution line fault monitoring devices under the transformer substation, judging that the confidence coefficient of the historical load data of the selected fault monitoring device meets a specific requirement, and keeping the selected fault monitoring device participating in fault positioning judgment. The process of determining the confidence requirement of the load data in step S22 includes the following steps, as shown in fig. 2:
a1: reading historical load data of a fault monitoring device;
a2: judging whether the historical ABC three-phase current balance degree in the historical load data is smaller than a set threshold value a, if yes, entering a step A3, and if not, entering a step A6;
a3: judging whether the ratio of the zero-sequence current amplitude to the maximum phase current in the historical load data is smaller than a set threshold b, if so, entering a step A4, otherwise, entering a step A6;
a4: judging whether the ABC three-phase currents in the historical load data are all larger than a set threshold value c, if so, entering the step A5, and if not, entering the step A6;
a5: the historical load data of the fault monitoring device meets the requirement of load data confidence;
a6: historical load data of the fault monitoring device does not meet the load data confidence requirement;
a7: and reading the historical load data of the next fault monitoring device and returning to the step A2. The historical load data of one fault monitoring device can be randomly read, and after the load data is judged according to the judgment condition required by the confidence degree of the load data, the historical load data of a new fault monitoring device which is not read is read. And the confidence of the historical load data result is that the ABC three-phase current is respectively greater than a set threshold value c according to the fact that the historical ABC three-phase current balance degree is less than a set threshold value a, the zero-sequence current amplitude/maximum phase current is less than a set threshold value b. Because the three-phase imbalance conditions of distribution networks with different structures and different loads are different, the setting threshold value a, the setting threshold value b and the setting threshold value c need to be adjusted adaptively according to the conditions of different distribution networks, and if the above 3 conditions are met, the confidence of the historical load data result of the fault monitoring device is met.
S3: calculating zero sequence break currents of all fault monitoring devices, and marking the fault monitoring devices with the zero sequence break currents exceeding a threshold value; as shown in fig. 3, step S3 includes the following steps:
s31: extracting amplitude and phase data of zero sequence current of the fault monitoring device meeting confidence level requirements;
s32: calculating the zero sequence current amplitude variation before and when the fault of each fault monitoring device occurs;
s33: sequencing the fault monitoring devices according to the variable quantity of the amplitude of the corresponding zero sequence current from large to small;
s34: setting a zero-sequence current mutation threshold value y;
s35: sequentially comparing the zero-sequence current amplitude variation of the fault monitoring device with a zero-sequence current mutation threshold value y according to the sequence;
s36: judging whether the zero sequence current amplitude variation of the fault monitoring device is larger than a zero sequence current mutation threshold value y, if so, entering a step S37, otherwise, entering a step S38;
s37: marking the fault monitoring devices for comparison, selecting the next fault monitoring device according to the sequence for comparison, and returning to the step S36;
s38: and recording and storing the marked fault monitoring device information. And extracting all fault monitoring device data with confidence degrees meeting the requirements to perform zero sequence current amplitude and phase comparison. And comparing the zero-sequence current amplitude and the phase before and when the fault occurs, and sequencing according to the zero-sequence current change amplitude from large to small. And if the zero sequence sudden change current of a certain fault monitoring device is larger than a threshold value, marking the fault monitoring device. The method comprises the steps of calculating zero-sequence current amplitude variation before and when faults of all fault monitoring devices occur, namely calculating abrupt current when the faults of all fault monitoring devices occur, sequencing the fault monitoring devices according to the corresponding zero-sequence current amplitude variation from large to small so as to be convenient to mark, when the fault monitoring devices are marked in sequence, the zero-sequence current amplitude variation of the front fault monitoring device is larger than an abrupt change threshold value y, and when the zero-sequence current amplitude variation of one fault monitoring device is detected to be smaller than the abrupt change threshold value y, the zero-sequence current amplitude variation of the rear fault monitoring device is smaller than the abrupt change threshold value y, so that the rear fault monitoring devices do not need to be searched and marked.
S4: and judging the fault line and the fault section according to the marked fault monitoring device. Step S4 includes the following steps:
s41: counting distribution lines to which the marked fault monitoring devices belong;
s42: judging whether the distribution lines to which the fault monitoring devices belong are the same, if so, entering a step S46, and if not, entering a step S43;
s43: judging whether the sudden change zero sequence current of each marked fault monitoring device flowing to the bus from the grounding point along the line has connectivity, if so, entering step S44, otherwise, entering step S45;
s44: keeping the mark that the sudden change zero sequence current has a connectivity fault monitoring device, and returning to the step S41;
s45: and eliminating the mark that the sudden change zero sequence current does not have a connectivity fault monitoring device, and returning to the step S41.
S46: selecting the distribution line as a ground fault line;
s47: calculating the distance from each marked fault monitoring device to the transformer substation;
s48: and judging the rear-section distribution line of the marking fault monitoring device farthest from the transformer substation as a ground fault section. Under the normal operation condition of a small current grounding system, zero sequence current and voltage cannot change suddenly but fluctuate within a certain range. When a permanent single-phase earth fault occurs, the direction of the zero-sequence current of the earth line flows from the earth point to the bus along the line, the amplitude and the phase of the zero-sequence current and the voltage of the fault monitoring device between the bus of the transformer substation and the fault point of the line are mutated, and the zero-sequence current and the voltage in a non-fault area are not mutated. And judging whether the marked fault monitoring devices belong to the same distribution line. If the lines are not the same, judging according to distribution network topological structure logic, judging whether the sudden change zero sequence current of the fault monitoring device flowing from the grounding point to the bus along the lines has connectivity or not, removing marks from the inconsistent fault monitoring devices, and then judging the distribution lines to which the marked fault monitoring devices belong again until the distribution lines to which the fault monitoring devices belong judge whether the lines are the same or not; and if the marked fault monitoring devices are all the lines A, selecting the ground fault line A as the line A, judging that the rear section of the marked fault monitoring device farthest from the transformer substation is a ground fault section according to the distribution network topological structure, setting the position of the marked fault monitoring device farthest from the transformer substation in the distribution line as an edge node of the fault section, and judging the distribution line, which is positioned at the node and far away from the transformer substation, in the distribution line as the ground fault section.
A small current ground fault finding and positioning system is disclosed, as shown in figure 4, and comprises a fault information collection module 1, wherein the fault information collection module 1 transmits data to a fault area positioning module 2, the fault information collection module 1 comprises a detection unit 3 for detecting the change condition of three-phase voltage of a distribution line and a data collection and transmission unit 4 for transmitting the data to the fault area positioning module 2, the fault area positioning module 2 comprises a confidence coefficient analysis unit 5, a zero sequence abrupt change current analysis unit 6 and a fault section judgment unit 7, the confidence coefficient analysis unit 5 is sequentially connected with the zero sequence abrupt change current analysis unit 6 and the fault section judgment unit 7, and the data collection and transmission unit 4 is respectively connected with the detection unit 3 and the confidence coefficient analysis unit 5. The fault information collection module 1 comprises a plurality of fault monitoring devices on the distribution line. This patent is based on present fault monitoring device function, and the inaccurate fault monitoring device's of preliminary treatment data is judged through multisource earth fault characteristic information fusion to and the mounted position of fault monitoring device in joining in marriage net topological structure, realize undercurrent earth fault circuit route selection and trouble section location, solve the unable earth fault locate function's of fault monitoring device defect. The method comprises the steps of automatically detecting three-phase voltage change through a fault information collection module 1, calling and storing load data of fault monitoring devices of all distribution lines under a transformer substation, sequentially judging the confidence of historical data and the amplitude of zero sequence current change of the collected load data of the fault monitoring devices through a confidence analysis unit 5 and a zero sequence break current analysis unit 6 in a fault region positioning module 2, preprocessing historical data, locking a fault section through a fault section judgment unit 7, and performing secondary processing on inaccurate data according to a distribution network topological structure when the fault section cannot be locked so as to determine the fault line and the fault section.
In order to overcome the defects that the zero sequence current transformer of the fault monitoring device has lower precision, the ground fault interval is easy to be misjudged due to the problems of product quality, installation and maintenance and the like, and the robustness is poor; because the fault monitoring device is exposed to the wind and rain outdoors and the product quality reason of the fault monitoring device, the problems that a part of fault monitoring devices acquire load data which is missed to be acquired and transmitted, and the ground fault is researched and judged by the data quality to a certain extent are solved.
According to the embodiment, the line selection and fault section positioning of the low-current ground fault line are realized through multi-source ground fault characteristic information fusion judgment, namely through the change of zero-sequence voltage and current amplitude and the change of phase fault characteristics before and after a fault and the installation position of a fault monitoring device in a distribution network topological structure, so that the power supply of a non-fault section is quickly recovered. And for the error historical data of the fault monitoring device, the historical data of the inaccurate fault monitoring device is preprocessed, after the zero-sequence current mutation value is calculated, the inaccurate data is processed for the second time according to the distribution network topological structure, the robustness of ground fault line and interval judgment is increased, the interval with the ground fault can be accurately searched, the rapid recovery of the power supply of the non-fault section is facilitated, and the power supply reliability is improved.
The above examples only show some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (6)
1. A small current ground fault searching and positioning method is characterized by comprising the following steps:
s1: detecting the three-phase voltage change by the fault monitoring device, and calling and testing and storing load data;
s2: extracting historical load data meeting the requirement of load data confidence;
s3: calculating zero sequence break currents of all fault monitoring devices, and marking the fault monitoring devices with the zero sequence break currents exceeding a threshold value;
s4: judging a fault line and a fault section according to the marked fault monitoring device;
the step S2 includes the following steps:
s21: reading historical load data of each fault monitoring device of the distribution line;
s22: judging whether the historical load data of each fault monitoring device meets the load data confidence requirement, if so, entering a step S24, and if not, entering a step S23;
s23: ignoring fault monitoring devices that do not meet load data confidence requirements;
s24: reserving and extracting historical load data of the fault monitoring device meeting the load data confidence requirement;
the process of determining the load data confidence requirement in step S22 includes the following steps:
a1: reading historical load data of a fault monitoring device;
a2: judging whether the historical ABC three-phase current balance degree in the historical load data is smaller than a set threshold value a, if so, entering the step A3, and if not, entering the step A6;
a3: judging whether the ratio of the zero-sequence current amplitude to the maximum phase current in the historical load data is smaller than a set threshold b, if so, entering a step A4, otherwise, entering a step A6;
a4: judging whether the three-phase currents ABC in the historical load data are all larger than a set threshold value c, if yes, entering a step A5, and if not, entering a step A6;
a5: the historical load data of the fault monitoring device meets the requirement of load data confidence;
a6: historical load data of the fault monitoring device does not meet the load data confidence requirement;
a7: the historical load data of the next fault monitoring device is read and the process returns to step a 2.
2. The small-current ground fault finding and positioning method according to claim 1, wherein the step S3 includes the steps of:
s31: extracting amplitude and phase data of zero sequence current of the fault monitoring device meeting confidence level requirements;
s32: calculating the zero sequence current amplitude variation before and when the fault of each fault monitoring device occurs;
s33: sequencing the fault monitoring devices according to the variable quantity of the amplitude of the corresponding zero sequence current from large to small;
s34: setting a zero-sequence current mutation threshold value y;
s35: sequentially comparing the zero-sequence current amplitude variation of the fault monitoring device with a zero-sequence current mutation threshold value y according to the sequence;
s36: judging whether the zero sequence current amplitude variation of the fault monitoring device is larger than a zero sequence current mutation threshold value y, if so, entering a step S37, otherwise, entering a step S38;
s37: marking the fault monitoring devices for comparison, selecting the next fault monitoring device according to the sequence for comparison, and returning to the step S36;
s38: and recording and storing the marked fault monitoring device information.
3. The small-current ground fault finding and positioning method according to claim 1 or 2, wherein the step S4 includes the following steps:
s41: counting distribution lines to which the marked fault monitoring devices belong;
s42: judging whether the distribution lines to which the fault monitoring devices belong are the same, if so, entering a step S46, and if not, entering a step S43;
s43: judging whether the sudden change zero sequence current of each marked fault monitoring device flowing to the bus from the grounding point along the line has connectivity, if so, entering step S44, otherwise, entering step S45;
s44: keeping the mark that the sudden change zero sequence current has a connectivity fault monitoring device, and returning to the step S41;
s45: rejecting the mark that the sudden change zero sequence current does not have a connectivity fault monitoring device, and returning to the step S41;
s46: selecting the distribution line as a ground fault line;
s47: calculating the distance from each marked fault monitoring device to the transformer substation;
s48: and judging the rear-section distribution line of the marking fault monitoring device farthest from the transformer substation as a ground fault section.
4. The small-current ground fault finding and positioning method according to claim 3, wherein the step S1 includes the following steps:
s11: detecting and calculating the variable quantity of each phase voltage of the distribution line by a fault monitoring device;
s12: setting a preset value x of the variable quantity of each phase voltage of the distribution line;
s13: judging whether the variation of each phase voltage of the distribution line exceeds a preset value x, if so, performing step S14, otherwise, returning to step S11;
s14: and (4) carrying out load data calling and storing on the fault monitoring devices of all distribution lines under the transformer substation.
5. A small current ground fault finding positioning system using any one of the small current ground fault finding positioning methods of claims 1-4, characterized by comprising a fault information collecting module (1), wherein the fault information collecting module (1) transmits data to a fault area positioning module (2), the fault information collecting module (1) comprises a detecting unit (3) for detecting the three-phase voltage variation of the distribution line and a data collecting and transmitting unit (4) for transmitting data to the fault area positioning module (2), the fault area positioning module (2) comprises a confidence degree analyzing unit (5), a zero sequence abrupt change current analyzing unit (6) and a fault area determining unit (7), the confidence degree analyzing unit (5) is sequentially connected with the zero sequence abrupt change current analyzing unit (6) and the fault area determining unit (7), the data collection and transmission unit (4) is respectively connected with the detection unit (3) and the confidence degree analysis unit (5).
6. The low current ground fault locating system according to claim 5, wherein the fault information collecting module (1) comprises a plurality of fault monitoring devices located on the distribution line.
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