CN117871936A - Bus protection CT disconnection distinguishing method and system considering zero sequence circulation - Google Patents
Bus protection CT disconnection distinguishing method and system considering zero sequence circulation Download PDFInfo
- Publication number
- CN117871936A CN117871936A CN202311815230.9A CN202311815230A CN117871936A CN 117871936 A CN117871936 A CN 117871936A CN 202311815230 A CN202311815230 A CN 202311815230A CN 117871936 A CN117871936 A CN 117871936A
- Authority
- CN
- China
- Prior art keywords
- current
- bus
- interval
- zero sequence
- phase
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 43
- 238000005070 sampling Methods 0.000 claims abstract description 127
- 238000004364 calculation method Methods 0.000 claims description 15
- 230000000737 periodic effect Effects 0.000 claims description 6
- 238000004870 electrical engineering Methods 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 18
- 230000007423 decrease Effects 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 2
- 230000017105 transposition Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
Landscapes
- Emergency Protection Circuit Devices (AREA)
Abstract
The invention discloses a bus protection CT disconnection distinguishing method and system considering zero sequence circulation, relating to the technical field of electrical engineering; comprising the following steps: acquiring three-phase current sampling values of each interval of a target power system; based on the three-phase current sampling value, calculating bus differential current, bus braking current, bus zero sequence differential current and each interval zero sequence current of a target power system; calculating the bus zero sequence current variation, the interval current variation and the interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current and the interval zero sequence current; judging bus CT disconnection of a target power system based on bus differential current, bus brake current and bus zero sequence differential current variation; and judging the CT disconnection of each interval of the target power system based on the bus differential flow, the current variation of each interval and the zero sequence current variation of each interval. The invention eliminates the influence of zero sequence circulation on the existing bus CT disconnection distinguishing method, and improves the reliability of the bus CT disconnection distinguishing method.
Description
Technical Field
The invention relates to the technical field of electrical engineering, in particular to a bus protection CT disconnection distinguishing method and system considering zero sequence circulation.
Background
The 3/2 wiring leads to that the load is not distributed evenly among the branches and the phases due to the unbalance of the resistances of the branches and the unbalance of the resistances of the different phases of the same branch, and the unbalanced zero sequence circulation exists at each interval during the normal operation of the system due to the large transmission capacity of the ultra-high voltage transformer substation. The relevant actual operation data show that the magnitude of the zero sequence current is proportional to the system crossing power. The zero sequence current with larger amplitude has larger influence on relay protection and automatic devices, and particularly can bring adverse influence on bus protection CT disconnection.
The same tower double loop suffers from the same problems as described above. Because of the arrangement form of double-circuit lines on the same tower and the influence of no transposition or incomplete transposition, parameters of each phase and each phase of the circuit are asymmetric, and unbalanced zero-sequence circulation exists in the double-circuit lines on the same tower during normal operation, and the judgment of protection is influenced by the zero-sequence current with larger amplitude, so that protection misoperation can be even caused.
Aiming at bus protection CT disconnection discrimination, most students focus on the following two points:
(1) Firstly, whether a bus generates a differential current and the braking current changes is carried out, if the conditions are met, whether a zero sequence current is present is judged, and if the conditions are met, the branch is locked to be a broken line branch. However, the CT disconnection judging method ignores the influence of unbalanced zero sequence loop current in each interval, and the zero sequence loop current exists under the normal system operation condition, and the mode of judging whether one path of zero sequence current exists or not is invalid, so that whether the CT disconnection exists in the bus cannot be judged correctly.
(2) Firstly judging whether a bus has differential current generation and braking current change, if the conditions are met, then judging each interval zero sequence current, and locking a branch with the largest zero sequence current as a CT broken line branch. Similarly, the CT disconnection judging method ignores the influence of unbalanced zero sequence loop current in each interval, and has a large zero sequence loop current in the normal system operation condition for ultra-high voltage with large power transmission, and the mode that the branch with the largest zero sequence current is the CT disconnection branch is invalid.
Disclosure of Invention
The invention aims to solve at least one technical problem and provide a bus protection CT disconnection distinguishing method and system considering zero sequence circulation.
In a first aspect, the embodiment of the invention provides a bus protection CT disconnection distinguishing method considering zero sequence circulation, which is applied to bus protection of a target power system; comprising the following steps: acquiring three-phase current sampling values of each interval of the target power system; based on the three-phase current sampling value, calculating bus differential current, bus braking current, bus zero sequence differential current and each interval zero sequence current of the target power system; calculating the bus zero sequence current variation, each interval current variation and each interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current and each interval zero sequence current; judging a bus CT disconnection of the target power system based on the bus differential current, the bus brake current and the bus zero sequence differential current variation; and judging each interval CT disconnection of the target power system based on the bus differential flow, the each interval current variation and the each interval zero sequence current variation.
Further, calculating the bus differential current and the bus braking current based on the three-phase current sampled values, comprising: the bus bar differential flow for each interval is calculated by the following calculation formula: wherein I is nAK Phase A current sampling value is the K sampling point of the nth interval; i nBK Phase B current sampling value is the K sampling point of the nth interval; i nCK C phase current sampling value of the K sampling point at the nth interval; i dAK 、I dBK 、I dCK Differential flow formed by the phase A, B, C of the K sampling points of each interval of the bus is respectively formed; />The effective value of the phase difference flow of the K-th sampling point A is obtained, and F () is a Fourier algorithm; />A phase difference stream effective value for a Kth sampling point B; />The phase difference flow effective value is the K sampling point C; the bus brake current for each interval is calculated based on the following equation:wherein I is fAK 、I fBK 、I fCK And braking currents formed by the Kth sampling point A, B, C phase of each interval of the bus.
Further, calculating the bus zero sequence current and the interval zero sequence currents based on the three-phase current sampling values includes: calculating the zero sequence current of each interval by the following formula: i 0nK ＝I nAK +I nBK +I nCK ，Wherein I is nAK Phase A current sampling value is the K sampling point of the nth interval; i nBK Phase B current sampling value is the K sampling point of the nth interval; i nCK C phase current sampling value of the K sampling point at the nth interval; i 0nK Zero sequence current sampling value of the Kth sampling point of the nth interval; />The zero sequence current effective value of the Kth sampling point of the nth interval; calculating a bus zero sequence difference stream by the following formula:wherein I is 0dK A zero sequence error stream is formed for the zero sequence current sampling value of the Kth sampling point,is the zero sequence error flow effective value of the Kth sampling point.
Further, calculating a bus zero sequence current variation, an interval current variation, and an interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current, and the interval zero sequence current, including: calculating the bus zero sequence differential flow variation based on the following formula:in (1) the->The zero sequence differential current effective value of the previous cycle wave bus; />The bus zero sequence differential flow variation is used; calculating the zero sequence current variation of each interval based on the following formula: />In (1) the->The effective value of the zero sequence current of the last cycle wave of the nth interval; />The zero sequence current variation is the nth interval; the respective interval current variation amounts are calculated based on the following formulas:in (1) the->An effective value of an A-phase current sampling value of a K-th sampling point at an nth interval; />The effective value of the B-phase current sampling value of the K-th sampling point at the nth interval; />C phase current sampling value of the K sampling point at the nth interval; />The effective value of the sampling value of the phase A current of the periodic wave on the nth interval; />The effective value of the sampling value of the B-phase current of the periodic wave on the nth interval; />The effective value of the sampling value of the C-phase current of the cycle wave is the nth interval; />Phase a current variation for the nth interval; />The current variation of phase B at the nth interval; />The n-th interval C phase current variation.
Further, based on the bus differential flow, the bus braking current and the bus zero sequence differential flow variation, determining the bus CT disconnection of the target power system includes: judging whether the descending amount of the bus brake current and the bus differential current respectively exceed a preset brake current threshold value and a preset CT broken line locking value; if so, judging whether the bus zero sequence flow variation exceeds a preset zero sequence flow variation threshold, and if so, judging that the bus CT disconnection working condition exists in the target power system.
Further, based on the bus differential flow, the interval current variation and the interval zero sequence current variation, determining the interval CT disconnection of the target power system includes: judging whether the zero sequence current variation of each interval exceeds a preset zero sequence current variation threshold value or not; if yes, judging whether only one phase of current has a differential flow or not based on the bus differential flow; if only one phase current has a differential current, judging that a single-phase CT disconnection working condition exists at intervals meeting a first judgment condition; the first determination condition includes: only the single-phase current reduction variation exceeds a preset current variation threshold or no current; if a difference stream exists between the two-phase currents, judging that a two-phase CT disconnection working condition exists at intervals meeting a second judging condition; the second determination condition includes: the two-phase current reduction variation exceeds the preset current variation threshold or does not flow.
Further, the method further comprises: judging whether the zero sequence current variation of each interval exceeds a preset zero sequence current variation threshold value or not; if not, judging that the three-phase CT disconnection working condition exists at intervals meeting the third judging condition; the third determination condition includes: the three-phase current reduction variation exceeds the preset current variation threshold or no current, and the three phases have differential current.
In a second aspect, the embodiment of the invention also provides a bus protection CT disconnection distinguishing system considering zero sequence circulation, which is applied to bus protection of a target power system; comprising the following steps: the device comprises an acquisition module, a first calculation module, a second calculation module, a first judgment module and a second judgment module; the acquisition module is used for acquiring three-phase current sampling values of each interval of the target power system; the first calculation module is used for calculating bus differential current, bus brake current, bus zero sequence differential current and each interval zero sequence current of the target power system based on the three-phase current sampling value; the second calculation module is used for calculating the bus zero sequence current variation, the interval current variation and the interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current and the interval zero sequence current; the first judging module is used for judging the bus CT disconnection of the target power system based on the bus differential current, the bus brake current and the bus zero sequence differential current variation; and the second judging module is used for judging each interval CT disconnection of the target power system based on the bus differential flow, each interval current variation and each interval zero sequence current variation.
Further, the first discriminating module is further configured to: judging whether the descending amount of the bus brake current and the bus differential current respectively exceed a preset brake current threshold value and a preset CT broken line locking value; if so, judging whether the bus zero sequence flow variation exceeds a preset zero sequence flow variation threshold, and if so, judging that the bus CT disconnection working condition exists in the target power system.
Further, the second discriminating module is further configured to: judging whether the zero sequence current variation of each interval exceeds a preset zero sequence current variation threshold value or not; if yes, judging whether only one phase of current has a differential flow or not based on the bus differential flow; if only one phase current has a differential current, judging that a single-phase CT disconnection working condition exists at intervals meeting a first judgment condition; the first determination condition includes: only the single-phase current reduction variation exceeds a preset current variation threshold or no current; if a difference stream exists between the two-phase currents, judging that a two-phase CT disconnection working condition exists at intervals meeting a second judging condition; the second determination condition includes: the two-phase current reduction variation exceeds the preset current variation threshold or does not flow; if not, judging that the three-phase CT disconnection working condition exists at intervals meeting the third judging condition; the third determination condition includes: the three-phase current reduction variation exceeds the preset current variation threshold or no current, and the three phases have differential current.
The invention provides a bus protection CT disconnection discriminating method and system considering zero sequence circulation, which can reliably identify single-phase and multi-phase CT disconnection of a bus under the zero sequence circulation working condition, eliminate the influence of zero sequence circulation on the existing bus CT disconnection discriminating method, improve the reliability of the bus CT disconnection discriminating method and ensure the safe and reliable operation of a power system.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following description will briefly introduce the drawings that are needed in the detailed description or the prior art, it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a bus protection CT disconnection discriminating method considering zero sequence circulation according to the embodiment of the invention;
FIG. 2 is a schematic diagram of a bus bar spacing according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a logic diagram for determining that a bus exists with CT disconnection according to an embodiment of the present invention;
FIG. 4 is a flowchart of a method for determining an interval CT disconnection according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a single-phase CT disconnection logic for judging a certain interval of a bus according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a logic diagram for determining a two-phase CT disconnection of a bus at a certain interval according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a three-phase CT disconnection logic for determining a certain interval of a bus according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a bus protection CT disconnection discriminating system which takes into account zero sequence circulation according to the embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
Fig. 1 is a flowchart of a bus protection CT disconnection discriminating method considering zero sequence loop current according to an embodiment of the present invention, which is applied to bus protection of a target power system. As shown in fig. 1, the method specifically includes the following steps:
step S102, three-phase current sampling values of each interval of the target power system are obtained.
Step S104, based on the three-phase current sampling value, calculating bus differential current, bus brake current, bus zero sequence differential current and each interval zero sequence current of the target power system.
And S106, calculating the bus zero sequence current variation, the interval current variation and the interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current and the interval zero sequence current.
And S108, judging the bus CT disconnection of the target power system based on the bus differential flow, the bus brake current and the bus zero sequence differential flow variation.
Step S110, judging each interval CT disconnection of the target power system based on the bus differential flow, each interval current variation and each interval zero sequence current variation.
Fig. 2 is a schematic diagram of a bus bar spacing according to an embodiment of the present invention. As shown in fig. 2, the bus bar of the target power system is provided with a plurality of intervals (four intervals are exemplified in fig. 2), and the bus bar end is provided with bus bar protection.
Specifically, in step S104, the bus bar differential flow for each interval is calculated by the following calculation formula:
wherein I is nAK Phase A current sampling value is the K sampling point of the nth interval; i nBK Is the nth intervalK sampling points B-phase current sampling values; i nCK C phase current sampling value of the K sampling point at the nth interval; i dAK 、I dBK 、I dCK Differential flow formed by the phase A, B, C of the K sampling points of each interval of the bus is respectively formed;the effective value of the phase difference flow of the K-th sampling point A is obtained, and F () is a Fourier algorithm; />A phase difference stream effective value for a Kth sampling point B; />The phase difference flow effective value is the K sampling point C;
the bus brake current for each interval is calculated based on the following equation:
wherein I is fAK 、I fBK 、I fCK And braking currents formed by the Kth sampling point A, B, C phase of each interval of the bus.
Calculating the zero sequence current of each interval by the following formula:
I 0nK ＝I nAK +I nBK +I nCK
wherein I is nAK Is the nth roomPhase A current sampling value at a K-th sampling point; i nBK Phase B current sampling value is the K sampling point of the nth interval; i nCK C phase current sampling value of the K sampling point at the nth interval; i 0nK Zero sequence current sampling value of the Kth sampling point of the nth interval;the zero sequence current effective value of the Kth sampling point of the nth interval;
calculating a bus zero sequence difference stream by the following formula:
wherein I is 0dK A zero sequence error stream is formed for the zero sequence current sampling value of the Kth sampling point,is the zero sequence error flow effective value of the Kth sampling point.
Specifically, in step S106, the bus zero sequence differential flow variation is calculated based on the following expression:
in the method, in the process of the invention,the zero sequence differential current effective value of the previous cycle wave bus; />The zero sequence differential flow variation of the bus;
calculating the zero sequence current variation of each interval based on the following formula:
in the method, in the process of the invention,the effective value of the zero sequence current of the last cycle wave of the nth interval; />The zero sequence current variation is the nth interval;
the amount of change in each interval current is calculated based on the following equation:
in the method, in the process of the invention,an effective value of an A-phase current sampling value of a K-th sampling point at an nth interval; />The effective value of the B-phase current sampling value of the K-th sampling point at the nth interval; />C phase current sampling value of the K sampling point at the nth interval; />The effective value of the sampling value of the phase A current of the periodic wave on the nth interval; />The effective value of the sampling value of the B-phase current of the periodic wave on the nth interval; />The effective value of the sampling value of the C-phase current of the cycle wave is the nth interval; />Phase a current variation for the nth interval;the current variation of phase B at the nth interval; />The n-th interval C phase current variation.
Fig. 3 is a schematic diagram of a logic diagram for determining that a bus exists in a CT disconnection according to an embodiment of the present invention. As shown in fig. 3, specifically, step S108 further includes the following steps:
step S1081, judging whether the descending amount of the bus brake current and the bus differential current respectively exceed a preset brake current threshold value and a preset CT broken line locking value; if so, the flow advances to step S1082.
Specifically, whether the bus brake current and the bus differential current meet the following conditions is judged:
|I fAK -I fAK-ΔT |≥I fset
or->Or->
Wherein I is fAK-ΔT For the braking current of the previous cycle bus, I fset In is a current secondary rated value, I, in is a preset braking current threshold value, and the value range is 0.02-0.05 In dset The value range is 0.05-20 In for the preset CT broken line locking value; and continuously m sampling points simultaneously meet the conditions, and judging that the bus brake current decreases and the bus differential current meets the conditions.
And S1082, judging whether the bus zero sequence flow variation exceeds a preset zero sequence flow variation threshold, and if so, judging that the bus CT disconnection condition exists in the target power system.
Specifically, whether the bus zero sequence differential flow variation meets the following conditions is judged:
wherein I is 0set And for presetting a zero sequence flow variation threshold, taking 0.02-0.05 In, and simultaneously meeting the internal constant value condition of the zero sequence flow variation of the bus by continuous m sampling points, and judging that the bus CT is broken.
Fig. 4 is a flowchart of a method for determining an interval CT disconnection according to an embodiment of the present invention. As shown in fig. 4, step S110 further includes the steps of:
step 1101, judging whether the zero sequence current variation of each interval exceeds a preset zero sequence current variation threshold; if yes, go to step S1102-step S1104; if not, step S1105 is performed.
Specifically, the condition of the zero sequence current variation of each interval of the bus is judged, specifically:
wherein I is 0set1 And for presetting a zero sequence current variation threshold, taking 0.02-0.05 In, and simultaneously meeting the conditions by continuous m sampling points, and judging that zero sequence current is increased at certain intervals.
Step S1102, judging whether only one phase of current has a differential flow or not based on the bus differential flow; if yes, step S1103 is executed; if not, step S1104 is performed.
Step S1103, if only one phase current has a differential current, determining that a single-phase CT disconnection condition exists at an interval satisfying the first determination condition; the first determination condition includes: only the single-phase current decreases the amount of change beyond a preset current change amount threshold or no current.
Specifically, fig. 5 is a schematic diagram of a logic diagram for determining a single-phase CT disconnection of a bus at a certain interval according to an embodiment of the present invention. As shown in fig. 5, taking the interval 1A phase CT disconnection shown in fig. 2 as an example, if only 1 phase has a differential current, and only the single-phase current reduction variation satisfies the threshold value or no current, determining that the interval single-phase CT disconnection and outputting corresponding disconnection information, specifically, when the following criterion equation (1) is satisfied and any one of the conditions of equation (2) and equation (3) is satisfied, determining that the interval single-phase CT disconnection:
wherein I is set In order to preset the current variation threshold, the value is 0.02-0.05 In, and the condition is met by m continuous sampling points at the same time, and the corresponding phase current is judged to be reduced at a certain interval.
Step S1104, if there is a difference current between the two phases of current, determining that a two-phase CT disconnection condition exists at an interval meeting a second determination condition; the second determination condition includes: the two-phase current decreases the amount of change and exceeds the preset current amount of change threshold or does not flow.
Specifically, fig. 6 is a schematic diagram of a logic diagram for determining a two-phase CT disconnection of a bus at a certain interval according to an embodiment of the present invention. As shown in fig. 6, taking the interval 2A, B two-phase CT disconnection shown in fig. 2 as an example, if there is a differential current between two phases, and if the two-phase current reduction variation satisfies the threshold value or no current, determining that the interval two-phase CT disconnection and outputting corresponding disconnection information, specifically, determining that the interval two-phase CT disconnection when the following criterion equation (4) is satisfied and any one of the conditions of equation (5) and equation (6) is satisfied:
step S1105, judging that a three-phase CT disconnection working condition exists at intervals meeting a third judgment condition; the third determination condition includes: the three-phase current reduction variation exceeds a preset current variation threshold or no current, and the three phases have differential current.
Specifically, fig. 7 is a schematic diagram of a logic diagram for determining a three-phase CT disconnection of a bus at a certain interval according to an embodiment of the present invention. As shown in fig. 7, taking the interval 3 three-phase CT disconnection shown in fig. 2 as an example, if the three-phase current decreases to meet the threshold value or no current and there is a differential current in three phases, determining that the interval three-phase CT disconnection is performed and outputting corresponding disconnection information, specifically, when the following criterion equation (7) is satisfied and any one of the conditions of equation (8) and equation (9) is satisfied, determining that the interval three-phase CT disconnection is performed:
as can be seen from the above description, the embodiment of the invention provides a bus protection CT disconnection discriminating method which takes into account zero sequence circulation, and the bus protection acquires sampling values of three-phase currents at intervals in real time; calculating a bus differential current, a bus brake current, a bus zero sequence current, each interval current variation, each interval zero sequence current variation and each zero sequence current variation according to the obtained three-phase current sampling values; based on the change working condition of the bus brake current, carrying out CT disconnection discrimination according to the bus zero sequence differential current change quantity and the bus differential current condition; and carrying out broken line branch and phase judgment according to the zero sequence current of each interval, the current variation of each interval and the bus differential current condition. The invention can reliably identify single-phase and multi-phase CT disconnection of the bus under the zero sequence circulation working condition, eliminates the influence of zero sequence circulation on the existing bus CT disconnection distinguishing method, improves the reliability of the bus CT disconnection distinguishing method, and ensures the safe and reliable operation of the power system.
Example two
Fig. 8 is a schematic diagram of a bus protection CT disconnection discriminating system according to an embodiment of the present invention, which is applied to bus protection of a target power system. As shown in fig. 8, the system includes: the system comprises an acquisition module 10, a first calculation module 20, a second calculation module 30, a first discrimination module 40 and a second discrimination module 50.
Specifically, the acquiring module 10 is configured to acquire three-phase current sampling values of each interval of the target power system.
The first calculation module 20 is configured to calculate a bus differential current, a bus braking current, a bus zero sequence current, and each interval zero sequence current of the target power system based on the three-phase current sampling values.
The second calculation module 30 is configured to calculate a bus zero sequence current variation, an interval current variation, and an interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current, and the interval zero sequence current.
The first discriminating module 40 is configured to discriminate a bus CT disconnection of the target power system based on the bus differential current, the bus brake current, and the bus zero sequence differential current variation.
The second discriminating module 50 is configured to discriminate each interval CT disconnection of the target power system based on the bus differential current, each interval current variation, and each interval zero sequence current variation.
Specifically, the first discriminating module 40 is further configured to:
judging whether the descending amount of the bus brake current and the bus differential current respectively exceed a preset brake current threshold value and a preset CT broken line locking value;
if so, judging whether the bus zero sequence flow variation exceeds a preset zero sequence flow variation threshold, and if so, judging that the bus CT disconnection working condition exists in the target power system.
Specifically, the second discriminating module 50 is further configured to:
judging whether the zero sequence current variation of each interval exceeds a preset zero sequence current variation threshold value or not;
if yes, judging whether only one phase of current has a differential flow or not based on the bus differential flow;
if only one phase current has a differential current, judging that a single-phase CT disconnection working condition exists at intervals meeting a first judgment condition; the first determination condition includes: only the single-phase current reduction variation exceeds a preset current variation threshold or no current;
if a difference stream exists between the two-phase currents, judging that a two-phase CT disconnection working condition exists at intervals meeting a second judging condition; the second determination condition includes: the two-phase current reduction variation exceeds a preset current variation threshold or does not flow;
if not, judging that the three-phase CT disconnection working condition exists at intervals meeting the third judging condition; the third determination condition includes: the three-phase current reduction variation exceeds a preset current variation threshold or no current, and the three phases have differential current.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (10)
1. A bus protection CT disconnection distinguishing method considering zero sequence circulation is characterized in that the method is applied to bus protection of a target power system; comprising the following steps:
acquiring three-phase current sampling values of each interval of the target power system;
based on the three-phase current sampling value, calculating bus differential current, bus braking current, bus zero sequence differential current and each interval zero sequence current of the target power system;
calculating the bus zero sequence current variation, each interval current variation and each interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current and each interval zero sequence current;
judging a bus CT disconnection of the target power system based on the bus differential current, the bus brake current and the bus zero sequence differential current variation;
and judging each interval CT disconnection of the target power system based on the bus differential flow, the each interval current variation and the each interval zero sequence current variation.
2. The method according to claim 1, characterized in that: calculating the bus differential current and the bus braking current based on the three-phase current sampled values, including:
the bus bar differential flow for each interval is calculated by the following calculation formula:
wherein I is nAK Phase A current sampling value is the K sampling point of the nth interval; i nBK Phase B current sampling value is the K sampling point of the nth interval; i nCK C phase current sampling value of the K sampling point at the nth interval; i dAK 、I dBK 、I dCK Differential flow formed by the phase A, B, C of the K sampling points of each interval of the bus is respectively formed;the effective value of the phase difference flow of the K-th sampling point A is obtained, and F () is a Fourier algorithm; />A phase difference stream effective value for a Kth sampling point B; />The phase difference flow effective value is the K sampling point C;
the bus brake current for each interval is calculated based on the following equation:
wherein I is fAK 、I fBK 、I fCK And braking currents formed by the Kth sampling point A, B, C phase of each interval of the bus.
3. The method according to claim 1, characterized in that: based on the three-phase current sampling values, calculating the bus zero sequence current and each interval zero sequence current comprises the following steps:
calculating the zero sequence current of each interval by the following formula:
I 0nK ＝I nAK +I nBK +I nCK
wherein I is nAK Phase A current sampling value is the K sampling point of the nth interval; i nBK Phase B current sampling value is the K sampling point of the nth interval; i nCK C-phase current sampling for the nth sampling point of the nth intervalA value; i 0nK Zero sequence current sampling value of the Kth sampling point of the nth interval;the zero sequence current effective value of the Kth sampling point of the nth interval;
calculating a bus zero sequence difference stream by the following formula:
wherein I is 0dK A zero sequence error stream is formed for the zero sequence current sampling value of the Kth sampling point,is the zero sequence error flow effective value of the Kth sampling point.
4. A method according to claim 3, characterized in that: calculating a bus zero sequence current variation, an interval current variation and an interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current and the interval zero sequence current, including:
calculating the bus zero sequence differential flow variation based on the following formula:
in the method, in the process of the invention,the zero sequence differential current effective value of the previous cycle wave bus; />The bus zero sequence differential flow variation is used;
calculating the zero sequence current variation of each interval based on the following formula:
in the method, in the process of the invention,the effective value of the zero sequence current of the last cycle wave of the nth interval; />The zero sequence current variation is the nth interval;
the respective interval current variation amounts are calculated based on the following formulas:
in the method, in the process of the invention,an effective value of an A-phase current sampling value of a K-th sampling point at an nth interval; />The effective value of the B-phase current sampling value of the K-th sampling point at the nth interval; />C phase current sampling value of the K sampling point at the nth interval; />The effective value of the sampling value of the phase A current of the periodic wave on the nth interval; />The effective value of the sampling value of the B-phase current of the periodic wave on the nth interval;the effective value of the sampling value of the C-phase current of the cycle wave is the nth interval; />Phase a current variation for the nth interval; />The current variation of phase B at the nth interval; />The n-th interval C phase current variation.
5. The method according to claim 1, characterized in that: based on the bus differential flow, the bus braking current and the bus zero sequence differential flow variation, judging the bus CT disconnection of the target power system, comprising the following steps:
judging whether the descending amount of the bus brake current and the bus differential current respectively exceed a preset brake current threshold value and a preset CT broken line locking value;
if so, judging whether the bus zero sequence flow variation exceeds a preset zero sequence flow variation threshold, and if so, judging that the bus CT disconnection working condition exists in the target power system.
6. The method according to claim 1, characterized in that: based on the bus differential flow, the interval current variation and the interval zero sequence current variation, judging the interval CT disconnection of the target power system, comprising:
judging whether the zero sequence current variation of each interval exceeds a preset zero sequence current variation threshold value or not;
if yes, judging whether only one phase of current has a differential flow or not based on the bus differential flow;
if only one phase current has a differential current, judging that a single-phase CT disconnection working condition exists at intervals meeting a first judgment condition; the first determination condition includes: only the single-phase current reduction variation exceeds a preset current variation threshold or no current;
if a difference stream exists between the two-phase currents, judging that a two-phase CT disconnection working condition exists at intervals meeting a second judging condition; the second determination condition includes: the two-phase current reduction variation exceeds the preset current variation threshold or does not flow.
7. The method according to claim 6, wherein: the method further comprises the steps of:
judging whether the zero sequence current variation of each interval exceeds a preset zero sequence current variation threshold value or not;
if not, judging that the three-phase CT disconnection working condition exists at intervals meeting the third judging condition; the third determination condition includes: the three-phase current reduction variation exceeds the preset current variation threshold or no current, and the three phases have differential current.
8. A bus protection CT disconnection distinguishing system considering zero sequence circulation is characterized in that the system is applied to bus protection of a target power system; comprising the following steps: the device comprises an acquisition module, a first calculation module, a second calculation module, a first judgment module and a second judgment module; wherein,
the acquisition module is used for acquiring three-phase current sampling values of each interval of the target power system;
the first calculation module is used for calculating bus differential current, bus brake current, bus zero sequence differential current and each interval zero sequence current of the target power system based on the three-phase current sampling value;
the second calculation module is used for calculating the bus zero sequence current variation, the interval current variation and the interval zero sequence current variation based on the three-phase current sampling value, the bus zero sequence current and the interval zero sequence current;
the first judging module is used for judging the bus CT disconnection of the target power system based on the bus differential current, the bus brake current and the bus zero sequence differential current variation;
and the second judging module is used for judging each interval CT disconnection of the target power system based on the bus differential flow, each interval current variation and each interval zero sequence current variation.
9. The system according to claim 8, wherein: the first judging module is further configured to:
judging whether the descending amount of the bus brake current and the bus differential current respectively exceed a preset brake current threshold value and a preset CT broken line locking value;
if so, judging whether the bus zero sequence flow variation exceeds a preset zero sequence flow variation threshold, and if so, judging that the bus CT disconnection working condition exists in the target power system.
10. The system according to claim 8, wherein: the second judging module is further configured to:
judging whether the zero sequence current variation of each interval exceeds a preset zero sequence current variation threshold value or not;
if yes, judging whether only one phase of current has a differential flow or not based on the bus differential flow;
if only one phase current has a differential current, judging that a single-phase CT disconnection working condition exists at intervals meeting a first judgment condition; the first determination condition includes: only the single-phase current reduction variation exceeds a preset current variation threshold or no current;
if a difference stream exists between the two-phase currents, judging that a two-phase CT disconnection working condition exists at intervals meeting a second judging condition; the second determination condition includes: the two-phase current reduction variation exceeds the preset current variation threshold or does not flow;
if not, judging that the three-phase CT disconnection working condition exists at intervals meeting the third judging condition; said first
The third determination condition includes: the three-phase current reduction variation exceeds the preset current variation threshold or no current,
three phases have differential flows.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311815230.9A CN117871936A (en) | 2023-12-26 | 2023-12-26 | Bus protection CT disconnection distinguishing method and system considering zero sequence circulation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311815230.9A CN117871936A (en) | 2023-12-26 | 2023-12-26 | Bus protection CT disconnection distinguishing method and system considering zero sequence circulation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN117871936A true CN117871936A (en) | 2024-04-12 |
Family
ID=90592787
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311815230.9A Pending CN117871936A (en) | 2023-12-26 | 2023-12-26 | Bus protection CT disconnection distinguishing method and system considering zero sequence circulation |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN117871936A (en) |
-
2023
- 2023-12-26 CN CN202311815230.9A patent/CN117871936A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102484365B (en) | A method of fault phase selection and fault type determination | |
| WO2007011710A2 (en) | An apparatus and method for identifying a loss of a current transformer signal in a power system | |
| CN109659917B (en) | Transient voltage-based multi-terminal flexible direct current line protection method and device | |
| CN114123253B (en) | Method, equipment and medium for monitoring three-phase load unbalance transformer area | |
| CN111679233B (en) | Method for positioning measurement abnormity of hybrid direct current engineering control system | |
| CN117871936A (en) | Bus protection CT disconnection distinguishing method and system considering zero sequence circulation | |
| CN109119972B (en) | Locking method and device for preventing differential misoperation caused by CT (current transformer) disconnection of balance winding | |
| CN112039036A (en) | Alternating current line instantaneous value variation distance protection method and system | |
| CN109088402B (en) | Time-domain full-waveform protection device for power transmission line and phase jump vector direction judgment method thereof | |
| CN113687188B (en) | Fault line selection method and device based on two-stage zero-sequence power change | |
| CN115267640A (en) | Current transformer abnormity checking method, system, equipment and medium | |
| CN110729705B (en) | Short-circuit protection method for direct-current transmission converter valve | |
| CN111273192B (en) | Fault backup protection method and device for converter of flexible direct current transmission system | |
| CN110350481B (en) | Differential protection method, system, equipment and storage medium of transformer | |
| CN109245057B (en) | Time domain full-waveform protection device for power transmission line and interphase mutation direction judgment method | |
| CN112531641B (en) | Active power distribution network differential protection method and system based on direct axis current | |
| CN112670951B (en) | Method and device for judging action of apparent power proportional differential element of phase-splitting transformer | |
| CN112698145B (en) | Fault distance measuring method and device suitable for power transmission line containing series reactor | |
| CN112350275B (en) | Current transformer disconnection identification method, protection method, medium and system | |
| CN112636469B (en) | Method for judging reliability of power grid transmission line operation load data | |
| CN113917279B (en) | Power distribution network fault phase distinguishing method and system and fault line distinguishing method and system | |
| CN117110783A (en) | Fault direction judging method and system based on current waveform distortion characteristics | |
| CN117949770A (en) | Method for diagnosing fault position causing common mode oscillation of flexible direct current system | |
| CN115902336A (en) | Method and system for calculating line capacitive reactance according to compensation voltage | |
| Chenna et al. | Fault Analysis of Three Level VSC-HVDC Connected Offshore Wind. |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |