CN107677920B - Ground fault indicator system considering different line parameters - Google Patents
Ground fault indicator system considering different line parameters Download PDFInfo
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Abstract
A ground fault indicator system considering different line parameters belongs to the technical field of power fault detection. The system comprises a fault indicator, a data aggregator and a master station. Coordination between a fault indicator and a master station. And judging by using the transient high-frequency component and the direct-current component. The judgment process is that the first group of fault indicator data of each outgoing line is processed, the high-frequency energy is improved through a correction formula to reduce the influence of different line parameters, and then the larger one of the improved high-frequency energy and the improved direct-current energy is selected to select the line. After the line selection is finished, the corresponding energy information of each group of fault indicators of the fault line is obtained by using the same steps, and when the energy information of the two groups of fault indicators meets the requirements, the fault can be judged to be generated between the two groups of fault indicators. The method has the advantages of reducing data processing amount, being suitable for a system with a plurality of neutral point contact type coexistence modes, and still having higher accuracy in the system with larger line length difference and larger line parameter difference.
Description
Technical Field
The invention belongs to the technical field of power fault detection, and particularly relates to a ground fault indicator system considering different line parameters.
Background
During the operation of the power system, faults often occur; wherein, the frequency of single-phase earth fault exceeds 80%. After a single-phase earth fault occurs, the fault current value has a great relationship with the system neutral point grounding mode; and the low-voltage distribution network in China mainly adopts a low-current grounding operation mode. When a single-phase earth fault occurs in a low-current earth system, the current flowing through the earth point is only line-to-earth capacitance current, and the value of the current is far smaller than the load current, so that a lot of difficulties are brought to fault detection. Therefore, single-phase ground faults are the most likely to occur but the most difficult to detect. Although according to relevant regulations, the small-current grounding system can continue to operate for 1-2 hours after single-phase grounding fault occurs; but the fault location is optionally found as soon as possible after the fault occurs.
In recent years, a plurality of devices for fault line selection and positioning are also in succession, and make great contribution to the reliable operation of a power system; among them, fault indicators disposed on overhead lines and cable lines are one type. After the fault indicator is provided, people continuously improve the fault detection method while upgrading the hardware. However, none of the fault indicators are suitable for use in a wide variety of power system conditions.
Therefore, in order to fully exert the function of the fault indicator, it is necessary to provide a fault indicator suitable for various working conditions. Namely, the high accuracy rate can be achieved under the condition that the neutral point grounding mode is not known.
Disclosure of Invention
The present invention aims to provide a ground fault indicator system taking into account different line parameters, which solves the above problems and utilizes line dc components and improved high frequency components for the judgment.
The invention comprises a fault indicator, a data aggregator and a master station.
The fault indicator and the data aggregator adopt a short-distance wireless communication technology, and the data aggregator receives signals of the fault indicators and then uniformly transmits the signals to the master station; this can reduce communication costs. This communication method is widely used now, and it is only a method for realizing communication between devices in the system, and is not intended as a protection content of the present invention. And the master station is the processing hub of the system. The invention is particularly concerned with the cooperation of a fault indicator with a primary station. Therefore, it will be described in detail below.
1) The fault indicator comprises a power supply module, a signal detection module, a storage module, a communication module, a control module and a fault indication module. The connection relationship is as follows: the power supply module is connected with other modules to provide working voltage and current of each module; the signal detection module is connected with the power supply module, the storage module and the control module; the storage module is connected with the power supply module, the signal detection module and the control module; the control module is connected with the power supply module, the signal detection module, the storage module, the communication module and the fault indication module; the communication module is connected with the power module and the control module; and the fault indication module is connected with the power supply module and the control module.
The power module supplies power for the whole fault indicator, and can take power from an overhead line or a cable line so as to ensure continuous and reliable operation of the fault indicator.
The signal detection module is used for collecting the current and the voltage to ground on the line and transmitting the data to the storage module for storage.
A memory module is where the line current and the voltage to ground are stored, which can transfer information for a certain period of time to the respective module according to the command requirements.
The communication module is responsible for communicating with other devices and can transmit and receive information and instructions.
The control module is the core of the fault indicator and is responsible for judging whether a ground fault occurs and coordinating the work among the modules of the fault indicator.
The fault indication module is a module capable of displaying the fault on site after determining that the position of the fault indicator has the fault, and can turn over the cards or emit light.
2) The main station is the core of the system and is responsible for processing data sent by each fault indicator and fault judgment, sending a control instruction to the fault indicator and sending position information of a fault location to maintenance personnel. And on the screen of the master station, the fault section can be visually seen.
The basic idea of the invention is to make a decision using a transient high frequency component and a direct current component. The judgment process is that the first group of fault indicator data of each outgoing line is processed, the high-frequency energy is improved through a correction formula to reduce the influence of different line parameters, and then the larger one of the improved high-frequency energy and the improved direct-current energy is selected to select the line. After the line selection is finished, the corresponding energy information of each group of fault indicators of the fault line is obtained by using the same steps, and when the energy information of the two groups of fault indicators meets the requirements, the fault can be judged to be generated between the two groups of fault indicators.
The invention has the advantages that the data processing amount is reduced, and the method is suitable for a system with a plurality of neutral point grounding modes coexisting without knowing the mode of grounding the neutral point of the system; the method has more applicable working conditions, and has higher accuracy in a system with larger line length difference and larger line parameter difference when the error of the mutual inductor is considered.
Drawings
Fig. 1 is a block diagram of a fault indicator according to the present invention.
Fig. 2 is a flow chart of the operation of the fault indicator.
FIG. 3 is a flowchart of the operation of the fault indicator master station.
Fig. 4 is a high-frequency energy diagram before improvement, wherein the initial fault phase angle is 30 degrees, and the grounding point resistance value is 30 omega.
Fig. 5 is a high-frequency energy diagram after the improvement of the initial fault phase angle of 30 degrees and the grounding point resistance value of 30 omega.
Fig. 6 is a high-frequency energy diagram before improvement, wherein the initial fault phase angle is 40 degrees, and the grounding point resistance value is 30 omega.
Fig. 7 is a high-frequency energy diagram after the improvement of the initial fault phase angle of 40 degrees and the grounding point resistance value of 30 omega.
Detailed Description
The invention comprises a fault indicator, a data aggregator and a master station.
The fault indicator and the data aggregator adopt a short-distance wireless communication technology, and the data aggregator receives signals of the fault indicators and then uniformly transmits the signals to the master station; this can reduce communication costs. This communication method is widely used now, and it is only a method for realizing communication between devices in the system, and is not intended as a protection content of the present invention. And the master station is the processing hub of the system. The invention is particularly concerned with the cooperation of a fault indicator with a primary station.
The working principle of the present invention will be further explained with reference to the attached drawings, and the fault indicator is installed on an overhead line or a cable line and then enters into a working state.
The fault indicator starts to sample the line current and voltage after entering a working state, the sampled current data are directly stored in the storage module, and the voltage data are stored in the storage module and simultaneously input into the control module to be simply judged.
1) And judging whether the current voltage value is continuously less than 0.5 time of the preset voltage in a half period, and if the current voltage value is less than 0.5 time of the preset voltage, judging that the phase where the fault indicator is located has a ground fault.
2) And if the current voltage lasts for half a period and is more than 1.5 times of the preset voltage, judging that the system has a ground fault, wherein the phase of the fault indicator is a non-fault phase. That is, when the system fails, all of the fault indicators will determine that the system has failed.
3) And after the system is judged to be in fault, the controller sends out a corresponding instruction. And extracting the current data of one period corresponding to the moment when the voltage falls or rises from the memory.
4) And inputting the current data of one cycle after the extracted fault occurs into a communication module, and finally transmitting the current data to the master station.
5) And after receiving the data transmitted by each fault indicator, the main station groups and stores the data according to the installed line.
6) According to the content, the zero sequence current transmitted by the first group of fault indicators of each outgoing line is solved. Namely, the zero sequence current of the line is calculated according to a group of fault indicator data of each outgoing line closest to the transformer substation.
7) And (5) solving FFT for the zero sequence current of each outgoing line. Then, the energy E of 300-3000Hz in the frequency spectrum of the line i is obtainedhi0And energy E in the line less than 20Hzdi。Ehi0And EdiReferred to as high frequency energy and dc energy, respectively.
8) According to the length l of each outgoing lineiFor high frequency energy Ehi0The improvement is that the high-frequency energy is EhiThe improved formula is as follows:
wherein n is the total number of outgoing lines,
the total length of all the outgoing lines,/iIs the length of line i, CnIs the capacitance to ground of line n.
9) Selecting two values E with the maximum high-frequency energy after improvement in each outgoing linehmiAnd EhmjCalculating the difference Δ E between the twohmNamely:
ΔEhm＝|Ehmi-hmj|
10) selecting two values E with the maximum direct current energy in each outgoing linedmiAnd EdmjCalculating the difference Δ E between the twodmNamely:
ΔEdm＝|Edmi-dmj|
11) comparison of Δ EhmAnd Δ EdmThe size of (2).
12) If Δ EhmRatio Delta EdmIf it is large, the next judgment is made by applying high frequency energy. I.e. the maximum high-frequency energy E in each outgoing linehmiThe corresponding line i is a faulty line. Fault line selection is completed, and fault location is performed in the next step:
① find zero sequence current at each fault indicator in line i, and similarly find high frequency energy E of each grouphip。
② setting i outgoing lines with k groups of fault indicators, each group corresponding to high frequency energy as Ehip，p＝1，2…k。
③, comparing the high frequency energy of each group on the i line, when the high frequency energy ratio of two adjacent fault indicators, z and x, is less than 0.7, then judging that the fault point is between the z group fault indicator and the x group fault indicator.
13) If Δ EhmRatio Delta EdmIf the current is small, the direct current energy is applied to carry out the next judgment. I.e. the maximum dc energy E in each outgoing linedmiThe corresponding line i is a faulty line. Fault line selection is completed, and fault location is performed in the next step:
① find zero sequence current at each fault indicator in line i, and similarly find DC energy E of each groupdip。
② setting i outgoing lines with k groups of fault indicators, each group corresponding to DC energy of Edip，p＝1，2…k。
③, comparing the DC energy of each group on the i line, when the DC energy ratio of two adjacent fault indicators z and x is less than 0.7, then judging that the fault point is between the z group fault indicator and the x group fault indicator.
14) Finally, the fault section will be displayed on the master screen. And the fault position information is sent to a mobile phone of a maintenance worker so as to find out the fault position as soon as possible.
The method can be detected through simulation, four outgoing lines are totally arranged in a simulation model, and one line is a fault line. Fig. 4 and fig. 5 are a comparison between before and after the improvement of the high-frequency energy, and it can be seen that the discrimination of the high-frequency energy between the lines is enhanced after the improvement, and the line selection is easy to fail.
Next, the methods before and after the improvement are compared, and tables 1 and 2 are data judged by a high-frequency energy method; tables 3 and 4 show the results of using the method proposed herein.
TABLE 1 line selection results of high frequency energy method in ungrounded systems
TABLE 2 line selection results of high-frequency energy method in arc suppression coil grounding system
Table 3 line selection results of the method herein in ungrounded systems
TABLE 4 line selection results of the method herein in a crowbar coil grounding system
Simulation proves that the fault indicator system utilizing the comprehensive criterion has high accuracy rate and does not influence the accuracy rate under the condition that the neutral point grounding mode is unknown; the influence of the fault initial phase angle on fault detection is greatly reduced, and high discrimination is provided when the capacitance value of the non-fault line to the ground is large, so that the occurrence of misjudgment is prevented; namely, the method is suitable for systems with larger line length difference and larger line parameter difference.
Claims (1)
1. A ground fault indicator system that takes into account different line parameters, comprising: the system comprises a fault indicator, a data collector and a master station; it is characterized in that the preparation method is characterized in that,
the fault indicator and the data aggregator adopt short-distance wireless communication, and the data aggregator receives signals of the fault indicators and then uniformly transmits the signals to the master station; to reduce communication costs; the main station is a processing center of the system; the cooperation between the fault indicator and the master station;
the fault indicator comprises a power supply module, a signal detection module, a storage module, a communication module, a control module and a fault indication module; the power supply module is connected with other modules to provide working voltage and current of each module; the signal detection module is connected with the power supply module, the storage module and the control module; the storage module is connected with the power supply module, the signal detection module and the control module; the control module is connected with the power supply module, the signal detection module, the storage module, the communication module and the fault indication module; the communication module is connected with the power module and the control module; the fault indication module is connected with the power supply module and the control module;
the power supply module supplies power to the whole fault indicator and takes power from an overhead line or a cable line so as to ensure the continuous and reliable operation of the fault indicator;
the signal detection module is used for collecting current and voltage to ground on a line and transmitting data to the storage module for storage;
the storage module is a place for storing the line current and the voltage to ground, and transmits information of a specific time period to the corresponding module according to the instruction requirement;
the communication module is responsible for communicating with other equipment, transmitting and receiving information and instructions;
the control module is the core of the fault indicator and is responsible for judging whether a ground fault occurs and coordinating the work among the modules of the fault indicator;
the fault indication module is a module capable of displaying a fault on site after determining that the position of the fault indicator has a fault, and turning cards or emitting light;
the master station is the core of the system and is responsible for processing data sent by each fault indicator and judging faults, sending control instructions to the fault indicators and sending position information of fault sites to maintenance personnel; visually finding out a fault section on a screen of a master station;
the fault indicator records and stores line data and judges that the system has a fault when the requirement is met; sending the fault information to a master station for processing through a data collector;
the main station is a center of data processing and judges by using a transient high-frequency component and a direct-current component; in the judging process, the zero sequence current at the first group of fault indicators of each outgoing line is firstly solved, the FFT is solved for the zero sequence current of each outgoing line, and then the energy E of 300-3000Hz in the frequency spectrum of the line i is solvedhi0And energy E in the line less than 20Hzdi， Ehi0And EdiReferred to as high frequency energy and direct current energy, respectively; according to the length l of each outgoing lineiFor high frequency energy Ehi0The improvement is that the high-frequency energy is EhiThe improved formula is as follows:
wherein n is the total number of outgoing lines,
the total length of all the outgoing lines,/iIs the length of line i, CnIs the capacitance to ground of line n;
selecting two values E with the maximum high-frequency energy after improvement in each outgoing linehmiAnd EhmjCalculating the difference Δ E between the twohm＝|Ehmi-Ehmj|；
Selecting the DC in each outletTwo values E of maximum energydmiAnd EdmjCalculating the difference Δ E between the twodm＝|Edmi-Edmj|；
Comparison of Δ EhmAnd Δ EdmThe size of (d);
if Δ EhmRatio Delta EdmIf it is large, the high frequency energy is applied to make the next judgment, i.e. the maximum high frequency energy E in each outgoing linehmiThe corresponding line i is a fault line; fault line selection is completed, and fault location is performed in the next step:
the zero sequence current of each group of fault indicators in the line i is calculated, and the high-frequency energy E of each group is calculated in the same wayhip；
Setting k groups of fault indicators on the i outgoing line, wherein the high-frequency energy corresponding to each group is Ehip，p＝1，2...k；
Comparing the high-frequency energy of each group on the i line when the high-frequency energy ratio of two adjacent fault indicators z and x
If the fault point is less than 0.7, the fault point is judged to be between the z group fault indicator and the x group fault indicator;
if Δ EhmRatio Delta EdmIf the DC energy is small, the DC energy is applied to carry out the next judgment, namely the maximum DC energy E in each outgoing linedmiThe corresponding line i is a fault line; fault line selection is completed, and fault location is performed in the next step:
the zero sequence current of each group of fault indicators in the line i is calculated, and the direct current energy E of each group is calculated in the same waydip；
Setting k groups of fault indicators on the i outgoing line, wherein the corresponding direct current energy of each group is Edip，p＝1，2...k；
Comparing the DC energy of each group on the i line, and comparing the DC energy of two adjacent fault indicators z and x when the DC energy of the two adjacent groups
Less than 0.7, the fault point is determined to be between z sets of fault indicators and x sets of fault indicatorsA (c) is added;
the system is suitable for a system with a plurality of neutral point grounding modes, and the mode of grounding the neutral point of the system is not required to be known.
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| CN202141778U (en) * | 2011-05-30 | 2012-02-08 | 上海励谙电子技术有限公司 | Line fault positioner used for 10kV power distribution network |
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