CN111969556B - Excitation inrush current judgment method and judgment device - Google Patents
Excitation inrush current judgment method and judgment device Download PDFInfo
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- CN111969556B CN111969556B CN202010813488.5A CN202010813488A CN111969556B CN 111969556 B CN111969556 B CN 111969556B CN 202010813488 A CN202010813488 A CN 202010813488A CN 111969556 B CN111969556 B CN 111969556B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0092—Details of emergency protective circuit arrangements concerning the data processing means, e.g. expert systems, neural networks
Abstract
The invention relates to the technical field of relay protection, in particular to a method and a device for judging magnetizing inrush current, which comprises the following steps: s10, collecting three-phase current Ip and three-phase voltage Up at a relay protection installation position; s20, analyzing at least one phase current in the three-phase current collected in the step S10, and calculating the proportion IZ of the effective value of the direct current component in the first cycle of the phase current to the effective value of the fundamental component; s30, calculating the three-phase voltage Up acquired in the step S10 to obtain a negative sequence voltage U2 and a zero sequence voltage U0; s40, judging a repressing condition; and S50, judging the excitation inrush current according to the direct current component proportion and the repressing condition. The invention is based on the DC component ratio and the composite voltage condition to distinguish: the method has the advantages that the magnetizing inrush current is judged by adopting the proportion of the direct current components, the accuracy is high, meanwhile, the composite voltage locking condition is considered, the fault current with the direct current components is screened out, the protection failure caused by the fact that the fault current has the direct current components is avoided, and the accuracy and the reliability of the magnetizing inrush current judgment can be improved.
Description
Technical Field
The invention relates to the technical field of relay protection, in particular to a method and a device for judging magnetizing inrush current.
Background
The relay protection is the first line of defense for safe and stable operation of the power grid, the reliable and correct action of the relay protection is directly related to the safety of the power grid and equipment, and when a power system breaks down, the current increase is the most obvious characteristic, so that the relay protection principle based on the fault current is the simplest and most common protection principle. However, in practice, when the transformer is switched on in an idle state, a large current may exist due to the excitation of the transformer, that is, an inrush current, which may cause malfunction of differential protection and overcurrent protection, and the existing protection with an inrush current determination function determines the inrush current by a method of waveform identification, including methods of a discontinuous angle, a method, a second harmonic, waveform fuzzy identification, and the like, and these methods have the following disadvantages: when a fault occurs, the protection action time is long, and in a distribution network line, the line may carry a plurality of distribution transformers to drop, and because excitation characteristics of the plurality of distribution transformers are inconsistent, some waveform identification methods are inaccurate in judgment.
Chinese patent CN107765077A discloses a magnetizing inrush current identification method based on attenuation characteristics of a direct current component of a transformer current, which includes the following steps: setting a time interval reference; calculating the amplitude ratio of the direct current component to the fundamental component of the outlet circuit breaker current of the high-voltage side and the medium-voltage side of the transformer; and logically judging the current data of the circuit breaker at the outlet of the transformer, identifying the magnetizing inrush current and the fault current and ensuring the accuracy of the differential protection action of the transformer. Although the magnetizing inrush current and the fault current can be identified by the scheme, the magnetizing inrush current and the fault current with the direct-current component cannot be distinguished, the judgment is inaccurate, and a large malfunction risk still exists.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a method and a device for judging magnetizing inrush current, which can effectively avoid protection misoperation and protection refusal caused by the magnetizing inrush current.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
provided is a method for judging magnetizing inrush current, which comprises the following steps:
s10, collecting three-phase current Ip and three-phase voltage Up at a relay protection installation position;
s20, analyzing at least one phase current in the three-phase currents collected in the step S10, and calculating the ratio IZ of the effective value of the direct-current component in the first cycle of the phase current to the effective value of the fundamental component;
s30, calculating the three-phase voltage Up acquired in the step S10 to obtain a negative sequence voltage U2 and a zero sequence voltage U0;
s40, carrying out re-pressing condition judgment: if the three-phase voltage Up is larger than the threshold value, the negative sequence voltage U2 is smaller than the threshold value and the zero sequence voltage U0 is smaller than the threshold value, determining that the complex voltage condition is satisfied, otherwise, determining that the complex voltage condition is not satisfied;
s50, judging the magnetizing inrush current according to the direct current component proportion and the repressing condition: and if the direct-current component ratio exceeds a threshold value and the re-voltage condition is met, judging that the excitation inrush current exists, and locking the related protection, otherwise, judging that the fault current exists and opening the related protection.
The invention discloses a method for judging magnetizing inrush current, which is characterized in that the judgment is carried out based on the proportion of direct current components and the condition of composite voltage: the method has the advantages that the direct-current component proportion with obvious characteristics in the magnetizing inrush current is used as the distinguishing condition, so that the accuracy of distinguishing the magnetizing inrush current is high, the composite voltage locking condition is considered, the fault current with the direct-current component can be accurately screened out, the protection refusal caused by the fact that the fault current has the direct-current component is avoided, the method can be suitable for the condition of switching on multiple transformers, and the accuracy and the reliability of distinguishing the magnetizing inrush current can be improved.
Preferably, the magnetizing inrush current discrimination function is switched on and off by a control word: 1 is input and 0 is output.
Preferably, in step S30, the zero sequence voltage U0 is obtained by performing a vector sum operation on the three-phase voltage Up.
Preferably, in step S30, the zero-sequence voltage U0 is obtained by an external zero-sequence voltage transformer.
Preferably, the voltage threshold Upm, the negative sequence voltage threshold U2m, the zero sequence voltage threshold U0m and the occupancy threshold Izm% in step S50 in step S40 can be set to different values according to different applications.
Preferably, the discrimination method can be applied to transformer protection or distribution network line automation terminal protection.
The invention also provides a computer readable storage medium, which comprises a magnetizing inrush current judging method program, and when the magnetizing inrush current judging method program is executed by a processor, the steps of the magnetizing inrush current judging method are realized.
The invention also provides a magnetizing inrush current judging device, which comprises a current measuring unit, a voltage measuring unit, a data processing unit, a data judging unit and a relay protection device, wherein the current measuring unit comprises a current measuring unit, a voltage measuring unit, a data processing unit, a data judging unit and a relay protection device:
the current measuring unit is used for acquiring a three-phase current Ip at the relay protection installation position, the voltage measuring unit is used for acquiring a three-phase voltage Up at the relay protection installation position, and the acquired three-phase current Ip and three-phase voltage Up are transmitted to the data processing unit;
the data processing unit receives and processes data collected by the current measuring unit and the voltage measuring unit to obtain a direct-current component ratio, a negative sequence voltage value and a zero sequence voltage value, and transmits the data obtained by calculation to the data judging unit;
the data discrimination unit receives the signal transmitted by the data processing unit and discriminates the magnetizing inrush current: and if the direct current component ratio exceeds the ratio threshold value Izm% and the re-voltage condition is met, determining that the direct current component ratio is an excitation inrush current, and locking the related protection, otherwise determining that the direct current component ratio is a fault current, and opening the related protection.
The invention relates to an excitation inrush current discrimination device, which discriminates based on a direct current component ratio and a composite voltage condition: because the proportion of the direct current component with obvious characteristics in the excitation surge current is used as a judging condition, the accuracy of judging the excitation surge current is high, the composite voltage locking condition is considered, the fault current with the direct current component can be accurately screened out, the protection refusal caused by the fact that the fault current has the direct current component is avoided, the method and the device can be suitable for the condition of switching on a plurality of transformers, and the accuracy and the reliability of judging the excitation surge current can be improved.
Further, an input end of the data determination unit is connected to an input unit, and the input unit is configured to set a voltage threshold Upm, a negative sequence voltage threshold U2m, a zero sequence voltage threshold U0m, and a duty threshold Izm%.
Further, the data discrimination unit is turned on and off by a control word: 1 is input, 0 is output.
Compared with the prior art, the invention has the beneficial effects that:
the invention relates to a method and a device for judging magnetizing inrush current, which are used for judging based on a direct current component ratio and a composite voltage condition: because the proportion of the direct current component with obvious characteristics in the excitation surge current is used as a judging condition, the accuracy of judging the excitation surge current is high, the composite voltage locking condition is considered, the fault current with the direct current component can be accurately screened out, the protection refusal caused by the fact that the fault current has the direct current component is avoided, the method and the device can be suitable for the condition of switching on a plurality of transformers, and the accuracy and the reliability of judging the excitation surge current can be improved.
Drawings
Fig. 1 is a flowchart of a magnetizing inrush current determination method according to the present invention;
fig. 2 is a schematic structural diagram of a magnetizing inrush current determination device according to the present invention.
Detailed Description
The present invention will be further described with reference to the following embodiments. Wherein the showings are for the purpose of illustration only and are shown by way of illustration only and not in actual form, and are not to be construed as limiting the present patent; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of the description, but it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation and operate, and therefore the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present patent, and it is possible for one of ordinary skill in the art to understand the specific meaning of the above terms according to the specific situation.
Example one
Fig. 1 shows an embodiment of a magnetizing inrush current determination method according to the present invention, which includes the following steps:
s10, collecting three-phase current Ip and three-phase voltage Up at a relay protection installation position;
s20, analyzing at least one phase current in the three-phase current collected in the step S10, and calculating the proportion IZ of the effective value of the direct current component in the first cycle of the phase current to the effective value of the fundamental component;
s30, calculating the three-phase voltage Up acquired in the step S10 to obtain a negative sequence voltage U2 and a zero sequence voltage U0;
s40, carrying out re-pressing condition judgment: if the three-phase voltage Up is greater than the voltage threshold value Upm, the negative sequence voltage U2 is less than the negative sequence voltage threshold value U2m and the zero sequence voltage U0 is less than the zero sequence voltage threshold value U0m, determining that the re-voltage condition is met, otherwise, determining that the re-voltage condition is not met;
s50, judging the magnetizing inrush current according to the direct current component proportion and the repressing condition: and if the direct current component ratio exceeds the ratio threshold value Izm% and the re-voltage condition is met, determining that the direct current component ratio is an excitation inrush current, and locking the related protection, otherwise determining that the direct current component ratio is a fault current, and opening the related protection.
Through the steps, the judgment is carried out based on the direct current component ratio and the composite voltage condition: because the proportion of the direct current component with obvious characteristics in the excitation surge current is used as a judging condition, the accuracy of judging the excitation surge current is high, the composite voltage locking condition is considered, the fault current with the direct current component can be accurately screened out, the protection refusal caused by the fact that the fault current has the direct current component is avoided, the method and the device can be suitable for the condition of switching on a plurality of transformers, and the accuracy and the reliability of judging the excitation surge current can be improved.
In one embodiment, the inrush current discrimination function is switched on and off by a control word: 1 is input, 0 is exit, the control logic is simple and easy to realize.
In one embodiment, in step S30, the zero-sequence voltage U0 is obtained by performing a vector sum operation on the three-phase voltages Up. In another embodiment, in step S30, the zero sequence voltage U0 is obtained by an external zero sequence voltage transformer. The acquisition mode of the zero sequence voltage U0 can be flexibly adjusted according to the configuration condition of the field voltage transformer, and the adaptability is strong.
In one embodiment, the voltage threshold Upm, the negative sequence voltage threshold U2m, the zero sequence voltage threshold U0m and the percentage threshold Izm% in step S50 in step S40 can be set to different values according to different applications. The voltage threshold value Upm, the negative sequence voltage threshold value U2m, the zero sequence voltage threshold value U0m and the ratio threshold value Izm% are not fixed and are manually set according to different application conditions, and the application range is wide.
In one embodiment, the discrimination method can be applied to transformer protection or distribution network line automation terminal protection.
Example two
The present embodiment is an embodiment of a computer-readable storage medium, where the computer-readable storage medium includes a magnetizing inrush current determination method program, and when the magnetizing inrush current determination method program is executed by a processor, the steps of the foregoing magnetizing inrush current determination method are implemented.
The computer readable storage medium of the embodiment stores the program of the discrimination method of the embodiment, which not only can accurately discriminate the magnetizing inrush current, but also can accurately screen out the fault current with the direct current component, thereby avoiding protection rejection caused by the fault current with the direct current component, being applicable to the condition of switching on a plurality of transformers, and improving the accuracy and reliability of the magnetizing inrush current discrimination.
EXAMPLE III
The embodiment is an embodiment of a magnetizing inrush current determination device, and includes a current measurement unit, a voltage measurement unit, a data processing unit, a data determination unit, and a relay protection device:
the current measuring unit acquires three-phase current Ip at the relay protection installation position, the voltage measuring unit acquires three-phase voltage Up at the relay protection installation position, and the acquired three-phase current Ip and three-phase voltage Up are transmitted to the data processing unit;
the data processing unit receives and processes the data collected by the current measuring unit and the voltage measuring unit to obtain a direct-current component ratio, a negative sequence voltage value and a zero sequence voltage value, and transmits the data obtained by calculation to the data judging unit;
the data discrimination unit receives the signal transmitted by the data processing unit and discriminates the magnetizing inrush current: and if the direct-current component ratio exceeds the ratio threshold value Izm% and the re-voltage condition is met, judging that the direct-current component ratio exceeds the ratio threshold value Izm%, and locking related protection, otherwise, judging that the direct-current component ratio exceeds the ratio threshold value and opening the related protection.
In the implementation of the embodiment, the judgment is carried out based on the direct current component ratio and the composite voltage condition, the direct current component ratio with obvious characteristics in the magnetizing inrush current is adopted as the judgment condition, the accuracy of judging the magnetizing inrush current is high, the composite voltage locking condition is considered, the fault current with the direct current component can be accurately screened out, and the protection refusal caused by the fact that the fault current has the direct current component can be effectively avoided.
In one embodiment, the input end of the data determination unit is connected to an input unit, and the input unit is configured to set a voltage threshold Upm, a negative sequence voltage threshold U2m, a zero sequence voltage threshold U0m, and a duty threshold Izm%. The voltage threshold value Upm, the negative sequence voltage threshold value U2m, the zero sequence voltage threshold value U0m and the proportion threshold value Izm% are not fixed and are manually set according to different application conditions, and the application range of the voltage threshold value Upm, the negative sequence voltage threshold value U2m, the zero sequence voltage threshold value U0m and the proportion threshold value Izm% are wide.
In one embodiment, the data discrimination unit is switched on and off by the control word: 1 is input, 0 is output. The switching is carried out by the control word, the control logic is simple, and the implementation is easy.
In the detailed description of the embodiments, various technical features may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A method for judging magnetizing inrush current is characterized by comprising the following steps:
s10, collecting three-phase current Ip and three-phase voltage Up at the relay protection installation position;
s20, analyzing at least one phase current in the three-phase current collected in the step S10, and calculating the proportion IZ of the effective value of the direct current component in the first cycle of the phase current to the effective value of the fundamental wave component;
s30, calculating the three-phase voltage Up acquired in the step S10 to obtain a negative sequence voltage U2 and a zero sequence voltage U0;
s40, judging the repressing condition: if the three-phase voltage Up is greater than the voltage threshold value Upm, the negative sequence voltage U2 is less than the negative sequence voltage threshold value U2m and the zero sequence voltage U0 is less than the zero sequence voltage threshold value U0m, determining that the re-voltage condition is met, otherwise, determining that the re-voltage condition is not met;
and S50, judging the magnetizing inrush current according to the direct current component ratio and the repressing condition: and if the direct current component ratio exceeds the ratio threshold value Izm% and the re-voltage condition is met, determining that the direct current component ratio is an excitation inrush current, and locking the related protection, otherwise determining that the direct current component ratio is a fault current, and opening the related protection.
2. The inrush current discrimination method according to claim 1, wherein the inrush current discrimination function is turned on and off by a control word: 1 is input and 0 is output.
3. The magnetizing inrush current determination method according to claim 1, wherein in step S30, the zero-sequence voltage U0 is obtained by performing a vector sum operation on the three-phase voltage Up.
4. The method according to claim 1, wherein in step S30, the zero-sequence voltage U0 is obtained by an external zero-sequence voltage transformer.
5. The method for determining the magnetizing inrush current according to claim 1, wherein the voltage threshold Upm, the negative sequence voltage threshold U2m, the zero sequence voltage threshold U0m, and the duty threshold Izm% in step S40 are set to different values according to different applications.
6. The magnetizing inrush current determination method according to any one of claims 1 to 5, wherein the determination method is applied to transformer protection or distribution network line automation terminal protection.
7. A computer-readable storage medium, characterized in that a magnetizing inrush current determination method program is included in the computer-readable storage medium, and when the magnetizing inrush current determination method program is executed by a processor, the steps of the magnetizing inrush current determination method according to any one of claims 1 to 6 are implemented.
8. A magnetizing inrush current determination device for implementing the magnetizing inrush current determination method according to any one of claims 1 to 6, comprising a current measurement unit, a voltage measurement unit, a data processing unit, a data determination unit, and a relay protection device:
the current measuring unit is used for acquiring a three-phase current Ip at the relay protection installation position, the voltage measuring unit is used for acquiring a three-phase voltage Up at the relay protection installation position, and the acquired three-phase current Ip and three-phase voltage Up are transmitted to the data processing unit;
the data processing unit receives and processes the data collected by the current measuring unit and the voltage measuring unit to obtain a direct current component ratio value, a negative sequence voltage value and a zero sequence voltage value, and transmits the data obtained by calculation to the data judging unit;
the data discrimination unit receives the signal transmitted by the data processing unit and discriminates the magnetizing inrush current: and if the direct current component ratio exceeds the ratio threshold value Izm% and the re-voltage condition is met, determining that the direct current component ratio is an excitation inrush current, and locking the related protection, otherwise determining that the direct current component ratio is a fault current, and opening the related protection.
9. The magnetizing inrush current determination device according to claim 8, wherein an input unit is connected to an input end of the data determination unit, and the input unit is configured to set a voltage threshold Upm, a negative sequence voltage threshold U2m, a zero sequence voltage threshold U0m, and a duty threshold Izm%.
10. The magnetizing inrush current determination device according to claim 8, wherein the data determination unit turns on and off by a control word: 1 is input, and 0 is input.
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