CN112240992A - Protection polarity verification method, device and equipment based on line empty charge transient current - Google Patents
Protection polarity verification method, device and equipment based on line empty charge transient current Download PDFInfo
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Abstract
The invention belongs to the field of power grid systems, and provides a method, a device and equipment for checking the polarity of line protection under no load, wherein the method comprises the following steps: extracting the transient current and the zero-mode current of each phase CT when the line is empty and charged, and calculating the corresponding effective value mean value; judging whether the polarity check starting criterion is met; if yes, judging whether a polarity error criterion is met; if the polarity error criterion is met, calculating error phase identification function values of all phases, wherein the phase with the minimum function value is the error phase; if one of the criteria is not satisfied, outputting a result with correct polarity. The invention can complete the polarity check of the secondary circuit of the line protection only by the idle charge transient current of one period when no load exists and the idle charge steady-state current is very weak, thereby effectively preventing the protection misoperation.
Description
Technical Field
The invention belongs to the field of power grid systems, and particularly relates to a protection polarity verification method, a protection polarity verification device and protection polarity verification equipment based on line empty charging transient current.
Background
The relay protection is the first defense line for the safe operation of the power grid, and the polarity of the relay protection device is the last defense line for ensuring the safe and stable operation of the relay protection device. With the increasing scale of the power grid, events of protection misoperation or abnormity caused by incorrect protection polarity happen in recent years.
Regarding the line protection polarity verification, the traditional method is that after the steady-state current of a measured line reaches a certain value, a protector measures the magnitude and the phase of each phase current on the secondary side of a CT (computed tomography) by using a clamp-type phase meter, and when the ABC three-phase currents are equal in magnitude and the phases sequentially differ by 120 degrees, the polarity can be judged to be correct. With the progress of science and technology, the sensitivity of the modern clamp type phase meter is greatly improved, and as long as the current with the magnitude of 10mA flows through the CT for the second time, the clamp type phase meter can accurately measure the phase of the current. Therefore, it is a prerequisite to adopt this polarity verification method to circulate a sufficiently large load current on the line.
And in actual engineering not all cases can effectively organize the load. For example, some newly built terminal stations are only connected by a single loop line, and the load cannot be directly dispatched from other places for polarity test. Under the condition, possible sources of the line protection polarity check current are life and construction loads in a factory and compensation equipment in a station. However, such loads tend to be quite limited. Or a rental load, but this is not economical.
Therefore, there are studies beginning to focus on polarity verification under no-load conditions. One method is to use the idle charge steady state current at line start up for verification. The principle of the method is that the capacitance current of the circuit still meets the three-phase symmetrical relation when the polarity is correct, so that the polarity can be verified by using the clamp type phase meter when the current meets the verification requirement of the clamp type phase meter, and the method is adopted by a small number of projects and has a good effect.
However, the magnitude of the current required in the method is greatly influenced by equipment parameters such as the length of the line, high impedance on the line and the like, and if the empty charge steady-state current does not meet the magnitude requirement, the polarity check cannot be carried out by using the clamp type phase meter.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a protection polarity verification method based on line empty charge transient current, and aims to solve the problem that the CT polarity verification of a line can not be realized when the line protection is in no load and the empty charge steady-state current is small in the prior art.
The invention provides a protection polarity verification method based on line empty charge transient current, which comprises the following steps:
s101, extracting transient currents and zero-mode currents of all phases of a secondary side of a circuit CT, and respectively calculating current average values of corresponding effective values;
s102, judging whether the current average value meets a polarity check starting criterion, if so, entering a step S103; if not, outputting the correct polarity of the three-phase CT;
s103, further judging whether the current average value meets a polarity error criterion, if so, entering a step S104, and if not, outputting a three-phase CT with correct polarity;
s104 calculates the error phase identification function value of each phase, and outputs the phase corresponding to the smallest function value as the error phase.
The checking method provided by the invention can accurately identify whether the protection polarity is correct or not, and can accurately judge the error phase when the protection polarity is wrong.
Further, the polarity check start criterion is I0-min(IA,B,C)≥0，I0Greater than or equal to IA，IB，ICAny current is the current meeting the polarity check starting criterion, wherein I0Is a zero mode current average value, IAIs the average value of transient current of A phase, IBIs the average value of transient current of B phase, ICAnd C-phase transient current average value.
Further, the polarity error criterion is
Wherein, IA,B,CRepresenting the mean value of the three-phase transient current, delta1Relative error threshold.
Further, in the present invention,
when xiA,B,C＝min(ξA,B,C) The corresponding error phase is obtained.
Further, the relative error threshold δ1Is less than or equal to 20.
Further, the relative error threshold δ1Preferably 20.
Further, in step S104, a polarity error warning is output and an error phase is displayed while outputting an error phase.
The invention also provides a protection polarity checking device based on the line empty charge transient current, which comprises: the circuit comprises a current extraction module, a polarity judgment module and a phase identification module, wherein the current extraction module is used for extracting each phase transient current and zero mode current of a secondary side of the circuit CT and respectively calculating a current average value of corresponding effective values; the polarity judgment module is used for judging whether the current average value meets polarity check starting criterion and polarity error criterion; the phase identification module is used for calculating error phase identification function values of all phases and outputting the phase corresponding to the minimum function value as an error phase.
Further, the polarity determination module comprises: the polarity check starting judgment unit is used for judging whether the current average value meets polarity check starting criteria; and the polarity error judgment unit is used for judging whether the current average value meets a polarity error criterion.
The invention also provides a protection polarity checking device based on the line empty charging transient current, which comprises a processor and a memory, wherein the processor comprises: the memory is used for storing program codes and transmitting the program codes to the processor; the processor is used for executing the protection polarity checking method according to the instructions in the program codes.
In the prior art, the basic principle of clamp type phase meter calibration is utilized to carry out digital sampling on the acquired current, then a microcomputer is applied to further process the information obtained by the digital sampling, and the fundamental wave phase of the current is extracted. When the polarity of the three-phase CT is correct, the ABC three-phase phases measured by using a pincer-type phase meter have a phase difference of 120 degrees in sequence; however, the measured current needs to be larger than 10mA, and the measurement process is a process of manually carrying out measurement and reading by a handheld device, which needs a long time, so that the transient current phase during empty charging cannot be accurately measured.
Transient currents, although short in duration, tend to be large; the transient current can be protected and accurately acquired as long as the minimum resolution of AD is met; the basic principle of the polarity test by using the empty charging transient current obtained by protection wave recording is as follows: in the empty charge transient process, according to the three-phase symmetrical relation, as long as the three-phase CT polarity is correct, the sum of instantaneous values of the three-phase transient current is 0 under the ideal condition. When the polarity is incorrect, the sum of the instantaneous values of the three-phase transient currents is ideally not 0. Therefore, the polarity check criterion can be constructed by utilizing the characteristics. In practice, due to errors caused by CT conversion, protection sampling, high-frequency noise interference in a transient process, and the like, the sum of the actual transient currents may not be 0. When the criterion threshold value needs to be constructed, a certain margin can be considered according to engineering experience. The invention solves the problem of the CT polarity check of the circuit when no load exists and the idle charge steady-state current is small.
Drawings
Fig. 1 is a flowchart illustrating an implementation of a protection polarity verification method based on line idle charge transient current according to an embodiment of the present invention;
FIG. 2 is an equivalent circuit and CT layout diagram of the on-site line during idle charging according to the embodiment of the present invention;
fig. 3 shows the test result of the method for checking the recording current of the Qiao Mao line during the empty charge state according to the embodiment of the present invention;
fig. 4 shows the results of the test performed by selecting the qiao mao line empty charge transient recording current verification method according to the embodiment of the present invention, when the phases a and b are reversed;
FIG. 5 shows the results of the measurement performed by selecting the Qiao Mao line empty charge transient recording current calibration method according to the embodiment of the present invention, and the B phase is reversed time measurement;
fig. 6 shows the results of the test performed by selecting the qiao mao line empty charge transient recording current verification method according to the embodiment of the present invention, where C phase is reversed time test.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Because the charging and discharging of the inductance and the capacitance exist during the empty charging of the circuit, the transient current peak value can reach the current of hundreds of mA and even A level; for the existing sampling module protected by the voltage class of 220kV and above, the AD minimum resolution is larger than 0.04 times of the rated current of the line (about 50 mA) under the limitation of sampling digit and range. For most lines, the transient current can be accurately collected by the protection, so that the polarity check criterion can be constructed by taking the correlation between the polarity and the empty charge transient current characteristic collected by the protection into consideration.
The invention provides a method for carrying out polarity verification by using line empty charge transient current, which can solve the problem of polarity verification of line protection under no load; the method specifically comprises the following steps:
1. and (3) switching on the circuit to be checked in an idle load mode, extracting the three-phase current and the zero-mode current of the secondary side of the circuit CT, obtaining the average value of the effective values, and entering the step 2.
Extracting three-phase current collected after closing and recording as iAi、iBi、iCi. The sum of the three is the zero modulus component, which is recorded as i0i. I.e. i0i＝iAi+iBi+iCiI represents the followingi sample points. The transient process is generally a power frequency period, a data window of half power frequency period is selected, and the effective value of each current in the window is calculated and recorded as IAj，IBj，ICj，I0j. Moving the data window according to a sampling interval, calculating the average value of the effective values of all the data windows when the data window moves a half period, and recording as IA，IB，IC，I0。
The effective value of each current in the jth data window is respectively as follows:
the average value of each current effective value is respectively:
wherein N is the number of sampling points in a power frequency period.
Description of the drawings: because the transient current has a large high-frequency component and is greatly influenced by the dispersion of the circuit breaker, etc., large high-frequency interference may be introduced. High-frequency interference can be suppressed through an effective value and average value algorithm.
2. And (4) judging whether the polarity verification starting criterion is met, and if so, entering the step 3 to further verify the polarity. If not, outputting a check result with correct polarity, and returning.
The polarity check starting criterion is I0-min(IA,B,C) Is more than or equal to 0. I.e. I0Greater than or equal to IA，IB，ICAny current is the current which meets the polarity check starting criterion.
Description of the drawings: when the polarity of the three-phase CT is correct, theoretically I is analyzed according to theory during the empty charging process0Always 0, when three-phase CT polarity has error, I0Is not 0. Therefore, when I0A difference of 0 is likely due to a three-phase CT polarity error. However, in practical engineering, high-frequency noise caused by CT transmission, protection sampling and transient process is generatedErrors due to disturbances, etc., in the actual transient process I0May not be 0, so that I is simply0If the value is 0, the polarity is not correct enough, so that a polarity check starting criterion is set, and unnecessary polarity check processes caused by interference are avoided as much as possible.
3. And (4) judging whether the polarity error criterion is met, and if so, entering the step 4 to identify the error phase. If not, outputting a check result with correct polarity, and returning.
The polarity error criterion is
Note the book
That is, the 2 times value of any phase current effective value is compared with zero mode current effective value, and the minimum value of relative error is not more than delta1% of the total amount of the protective agent is regarded as having polarity errors. According to a large number of actual line air-charged current recording tests, delta 120 can meet the verification requirement.
Description of the drawings: in the three-phase CT polarity test error type, because one-phase errors are equivalent to two-phase errors. So there are only three possible types of errors, namely: phase a error, phase B error, phase C error. In theory, the inference is made that the sum of the three-phase currents is 0: if there is a phase error, the effective value of the zero-mode current should be 2 times that of the phase current with the wrong polarity, so that the corresponding xiA,B,CWill be very small, conversely, in the absence of polarity errors, ξA,B,CIt will be very large. The polarity error criterion is designed.
4. And calculating the error phase identification function value of each phase, obtaining the phase with the minimum function value as the error phase, outputting the error phase identification result and returning.
The invention utilizes the empty charge transient state current obtained by protection wave recording to carry out polarity test, and the three-phase transient state current satisfies the condition that the sum of instantaneous values is 0 under an ideal condition according to the three-phase symmetrical relation in the empty charge transient state process as long as the three-phase CT has correct polarity. When the polarity is incorrect, the sum of the instantaneous values of the three-phase transient currents is ideally not 0. Therefore, the polarity check criterion can be constructed by utilizing the characteristics. In practice, due to errors caused by CT conversion, protection sampling, high-frequency noise interference in a transient process, and the like, the sum of the actual transient currents may not be 0. Certain margin can be considered according to engineering experience when constructing the criterion threshold value. The checking method provided by the invention can accurately identify whether the protection polarity is correct or not, and can accurately judge the error phase when the protection polarity is wrong.
To further illustrate the protection polarity verification method based on line idle charge transient current according to the embodiments of the present invention, the following is detailed with reference to the accompanying drawings and specific examples:
fig. 2 shows equivalent circuits and CT arrangement conditions during on-site line empty charging, and in the embodiment of the invention, a qiao mao line empty charging transient recording current is selected to test the verification method.
And testing when the ABC three phases are connected reversely respectively and the wiring is correctly performed, wherein the red, the green and the yellow correspond to the three phases respectively.
Correct wiring (as shown in fig. 3):
ABC three-phase relative error xiA,B,C243.58%, 97.53% and 157.59% are respectively higher than the 20% threshold value, and the polarity is judged to be correct.
A is directly opposite (as shown in fig. 4):
ABC three-phase relative error xiA,B,CRespectively as follows: 14.19%, 34.35% and 14.39%. If the A phase is lower than the 20% threshold value and the error is minimum, the polarity of the A phase is judged to be wrong.
B is directly opposite (as shown in fig. 5):
ABC three-phase relative error xiA,B,CRespectively as follows: 51.29%, 13.02% and 13.43%. If the phase B is lower than the threshold value of 20 percent and the error is minimum, the polarity of the phase B is judged to be wrong.
C is directly opposite (as shown in fig. 6):
ABC three-phase relative error xiA,B,CRespectively as follows: 22.39%, 29.64%, 8.24%. And if the C phase is lower than the 20% threshold value and the error is minimum, judging that the polarity of the C phase is wrong.
Therefore, under various conditions, the provided checking method can accurately identify whether the protection polarity is correct or not, and can accurately judge the error phase when the protection polarity is wrong. The idle charge steady-state current of the line is only about 3mA, and polarity verification cannot be performed by using the clamp type phase meter. The superiority of the invention for polarity verification by using the empty charge transient current is illustrated. The idle charge steady-state current of the line is only about 3mA, and polarity verification cannot be performed by using the clamp type phase meter. The superiority of the present document for polarity verification with empty charge transient current is illustrated. By adopting the transient current checking method provided by the research, the polarity of the transient current generated by the empty charge of 5 lines is checked, and the checking result is shown in the following table 1. Therefore, the method can accurately identify various conditions, and the verification effect is good.
TABLE 1 results of the verification of each line by the method
The invention also provides a protection polarity checking device based on the line empty charge transient current, which comprises: the circuit comprises a current extraction module, a polarity judgment module and a phase identification module, wherein the current extraction module is used for extracting each phase transient current and zero mode current of a secondary side of the circuit CT and respectively calculating a current average value of corresponding effective values; the polarity judgment module is used for judging whether the current average value meets polarity check starting criterion and polarity error criterion; the phase identification module is used for calculating error phase identification function values of all phases and outputting the phase corresponding to the minimum function value as an error phase.
Wherein, polarity judgement module includes: the polarity check starting judgment unit is used for judging whether the current average value meets polarity check starting criteria; and the polarity error judgment unit is used for judging whether the current average value meets a polarity error criterion.
The invention also provides a protection polarity checking device based on the line empty charging transient current, which comprises a processor and a memory, wherein the processor comprises: the memory is used for storing the program codes and transmitting the program codes to the processor; the processor is used for executing the protection polarity checking method according to instructions in the program codes.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A protection polarity verification method based on line idle charge transient current is characterized by comprising the following steps:
s101, extracting transient currents and zero-mode currents of all phases of a secondary side of a circuit CT, and respectively calculating current average values of corresponding effective values;
s102, judging whether the current average value meets a polarity check starting criterion, if so, entering a step S103; if not, outputting the correct polarity of the three-phase CT;
s103, further judging whether the current average value meets a polarity error criterion, if so, entering a step S104, and if not, outputting a three-phase CT with correct polarity;
s104 calculates the error phase identification function value of each phase, and outputs the phase corresponding to the smallest function value as the error phase.
2. The protection polarity verification method of claim 1, wherein the polarity verification start criterion is I0-min(IA,B,C)≥0，I0Greater than or equal to IA，IB，ICAt any current isMeets a polarity check start criterion, wherein I0Is a zero mode current average value, IAIs the average value of transient current of A phase, IBIs the average value of transient current of B phase, ICAnd C-phase transient current average value.
3. A method for protection polarity check according to claim 1 or 2, characterized in that said polarity error criterion is
Wherein, IA,B,CRepresenting the mean value of the three-phase transient current, delta1Relative error threshold.
4. The protection polarity verification method of claim 3,
when xiA,B,C＝min(ξA,B,C) The corresponding error phase is obtained.
5. A protection polarity verification method according to any one of claims 3 to 4, characterized in that the relative error threshold δ1Is less than or equal to 20.
6. The protection polarity verification method of claim 5, wherein the relative error threshold δ1Preferably 20.
7. The protection polarity verification method of any one of claims 1 to 6, wherein in step S104, a polarity error warning is output and an error phase is displayed at the same time as the output of the error phase.
8. The utility model provides a protection polarity verifying attachment based on circuit empty charge transient state electric current which characterized in that includes:
the current extraction module is used for extracting transient currents and zero-mode currents of all phases of the secondary side of the line CT and respectively calculating current average values of corresponding effective values;
the polarity judgment module is used for judging whether the current average value meets polarity check starting criteria and polarity error criteria;
and the phase identification module is used for calculating the error phase identification function value of each phase and outputting the phase corresponding to the minimum function value as the error phase.
9. The protection polarity verification apparatus of claim, wherein the polarity determination module comprises:
the polarity check starting judgment unit is used for judging whether the current average value meets polarity check starting criteria;
and the polarity error judgment unit is used for judging whether the current average value meets a polarity error criterion.
10. A protection polarity verification device based on line empty charge transient current, the device comprising a processor and a memory:
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to perform the protection polarity checking method of any one of claims 1 to 7 according to instructions in the program code.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117388575A (en) * | 2023-12-11 | 2024-01-12 | 广东威恒输变电工程有限公司 | Data vector testing method and system for current transformer of power supply and distribution system |
| CN117388575B (en) * | 2023-12-11 | 2024-03-19 | 广东威恒输变电工程有限公司 | Data vector testing method and system for current transformer of power supply and distribution system |
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