CN112072610B - Breaker failure protection optimization method and system based on comprehensive difference - Google Patents
Breaker failure protection optimization method and system based on comprehensive difference Download PDFInfo
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- CN112072610B CN112072610B CN202010785735.5A CN202010785735A CN112072610B CN 112072610 B CN112072610 B CN 112072610B CN 202010785735 A CN202010785735 A CN 202010785735A CN 112072610 B CN112072610 B CN 112072610B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/05—Details with means for increasing reliability, e.g. redundancy arrangements
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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
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/021—Details concerning the disconnection itself, e.g. at a particular instant, particularly at zero value of current, disconnection in a predetermined order
Abstract
The invention discloses a breaker failure protection optimization method and system based on comprehensive difference, wherein the method comprises the steps of identifying CT trailing current when a breaker is switched off near a current 90 degrees and near a current zero crossing point; if the CT trailing current is identified, the circuit breaker failure protection is controlled to return in a delayed mode, and tripping does not occur. The method can quickly and correctly judge the CT trailing, so that the failure protection of the circuit breaker is delayed and returned, the failure duration time after the circuit breaker fails is shortened, and the influence on the system stability is reduced.
Description
Technical Field
The invention relates to the field of relay protection of power systems, in particular to a breaker failure protection optimization method and system based on comprehensive difference.
Background
The breaker failure protection is backup protection widely used in relay protection, and is mainly used for protection configuration that a breaker cannot trip a fault due to correct action of main protection under the condition of the fault of a power system.
With the development of power grids in China, the electrical distance between each node is closer and closer, and the requirement of a system on the limit cutting time of a fault is shorter. The power grid in China has the characteristics of long distance, large capacity and parallel operation of alternating current and direct current, so that the problem is more prominent, and once the circuit breaker fails to operate, the system stability is greatly damaged.
Disclosure of Invention
In view of this, an object of the embodiment of the present application is to provide a method and a system for optimizing breaker failure protection based on comprehensive difference, which can quickly and correctly determine CT tailing, so that the time delay of breaker failure protection is returned, the fault duration after the breaker failure is shortened, and the influence on the system stability is reduced.
In a first aspect, an embodiment of the present application provides a circuit breaker failure protection optimization method based on comprehensive difference, including:
and (3) forming a logical OR of a cosine criterion and a full-period criterion, and identifying the current as the CT trailing current if any action of the cosine criterion and the full-period criterion is performed.
If the CT trailing current is identified, the circuit breaker failure protection is controlled to return in a delayed mode, and tripping does not occur.
With reference to the first aspect, this embodiment provides a first possible implementation manner of the first aspect, where the performing a logical or between a cosine criterion and a whole-cycle criterion, and identifying that the current is a CT trailing current includes:
if the cosine criterion acts, the current is judged to be CT trailing current when the circuit breaker is switched off near the zero crossing point.
If the criterion is operated all the round, the current is judged to be CT trailing current when the circuit breaker is disconnected nearby 90 degrees.
With reference to the first aspect, an embodiment of the present application provides a second possible implementation manner of the first aspect, where the cosine criterion calculation method includes:
and calculating a 2-point cosine difference proportion result, and judging that the amplitude of the 2-point cosine difference is increased in a short time when the circuit breaker is switched off near the current zero crossing point, so that the current is CT trailing current.
And calculating a 1-point full-cycle difference proportion result, and when the circuit breaker is switched off near the current 90 degrees or near a zero crossing point, the 1-point full-cycle difference does not have amplitude increase.
And forming a logical AND by the 2-point cosine differential proportion result and the 1-point full-cycle differential proportion result to form a cosine criterion, and identifying the CT trailing current when the circuit breaker is switched off near the current zero crossing point.
With reference to the first aspect, an embodiment of the present application provides a third possible implementation manner of the first aspect, where the method for calculating the weekly criterion includes:
and calculating a full-period Fourier proportion result, when the circuit breaker is disconnected near the current 90 degrees, the full-period Fourier generation short-time amplitude value is increased, and the current is judged to be CT trailing current.
And calculating a 1-point full-cycle difference proportion result, and when the circuit breaker is switched off near the current 90 degrees or near a zero crossing point, the 1-point full-cycle difference does not have amplitude increase.
And (3) forming a logical AND by the 1-point full-cycle difference proportion result and the full-cycle Fourier proportion result to form a full-cycle criterion, and identifying the CT trailing current when the circuit breaker is disconnected near the current 90 degrees.
With reference to the first aspect, an embodiment of the present application provides a fourth possible implementation manner of the first aspect, where the full-circled fourier scale result is calculated by calculating a full-circled fourier current time calculation result
Calculating the pre-week calculation of full-week Fourier
According to the formula
Carrying out proportional operation to identify the current variation trend, if the current variation trend is larger than a full-period Fourier proportion threshold, indicating that the current is the CT trailing current when the breaker is disconnected, and carrying out full-period Fourier action (the value of the full-period Fourier proportion threshold is
Value of (d).
The calculation method of the 2-point cosine difference proportion result comprises the steps of calculating the 2-point cosine difference calculation result of the current moment
Calculating 2-point cosine difference calculation result before current one circle
According to the formula
Carrying out proportional operation, identifying the current variation trend, if the current variation trend is greater than a 2-point cosine differential proportional threshold, indicating that the current is the CT trailing current when the circuit breaker is disconnected, and carrying out 2-point cosine differential action (the value of the 2-point cosine differential proportional threshold is MK) cos2 Value of (d).
The calculation method of the 1-point full-cycle difference proportion result comprises the steps of calculating the 1-point full-cycle difference calculation result of the current at the current moment
Calculating the 1-point full-cycle difference calculation result before one cycle of current
According to the formula
Carrying out proportional operation, identifying the current variation trend, and if the current variation trend is smaller than a 1-point full-cycle differential ratio threshold, carrying out 1-point full-cycle differential action (the value of the 1-point full-cycle differential ratio threshold is MK) diff1 Value of (d).
In a second aspect, the present application further provides a circuit breaker failure protection optimization system based on comprehensive difference, which is used for implementing the circuit breaker failure protection optimization method based on comprehensive difference as described above, and includes:
and the identification device is used for identifying the CT tail current when the breaker is opened near the current 90 degrees and near the current zero crossing point.
And the control device is used for controlling the circuit breaker failure protection to return in a delayed mode without tripping when the CT trailing current is identified.
With reference to the second aspect, embodiments of the present application provide a first possible implementation manner of the second aspect, where the identification apparatus includes:
and the full-period Fourier calculation module is used for calculating a full-period Fourier proportion result, and when the circuit breaker close to the current 90 degrees is disconnected, the full-period Fourier generation short-time amplitude value is increased, and the current is judged to be CT trailing current.
And the 2-point cosine difference calculating module is used for calculating a 2-point cosine difference proportion result, and when the circuit breaker near the current zero crossing point is switched off, the 2-point cosine difference is subjected to short-time amplitude increase and is judged as CT trailing current.
The 1-point full-cycle difference calculating module is used for calculating a 1-point full-cycle difference proportion result, and when the circuit breaker is switched off near the current 90 degrees or near a zero crossing point, the 1-point full-cycle difference does not have amplitude values increased;
and the cosine criterion module is used for forming a logical AND of the 2-point cosine differential proportion result and the 1-point full-cycle differential proportion result to form a cosine criterion and identifying the CT trailing current when the circuit breaker is switched off near the current zero crossing point.
And the whole-cycle criterion module is used for forming a logical AND of the 1-point whole-cycle differential proportion result and the whole-cycle Fourier proportion result to form a whole-cycle criterion and identifying the CT trailing current when the circuit breaker is disconnected at a current of 90 degrees.
With reference to the second aspect, embodiments of the present application provide a second possible implementation manner of the second aspect, where the full-circle fourier computing module includes:
a whole-cycle Fourier current time calculating unit for calculating the whole-cycle Fourier current time calculating result
A week-before-full-Freund calculation unit for calculating the week-before-full-Freund calculation result
A full-period Fourier proportion operation unit for calculating the ratio according to the formula
Performing proportional operation, identifying current variation trend, and if the current variation trend is greater than a proportional threshold
The whole cycle Fourier action.
With reference to the second aspect, an embodiment of the present application provides a third possible implementation manner of the second aspect, where the 2-point cosine difference calculating module includes:
a 2-point cosine difference current time calculation unit for calculating the current time calculation result of the 2-point cosine difference
A 2-point cosine difference one-cycle-before calculation unit for calculating 2-point cosine difference one-cycle-before calculation result
A 2-point cosine difference proportional operation unit for calculating the ratio of the cosine difference
Carrying out proportional operation, identifying the current variation trend, and if the current variation trend is larger than a proportional threshold MK cos2 Then 2-point cosine differential action.
With reference to the second aspect, an embodiment of the present application provides a fourth possible implementation manner of the second aspect, where the 1-point full-cycle difference calculating module includes:
a 1-point all-round difference current time calculation unit for calculating the current time calculation result of the 1-point all-round difference
A 1-point all-round difference one-week-ahead calculation unit for calculating the 1-point all-round difference one-week-ahead calculation result
A 1-point full-cycle differential proportional operation unit for calculating
Performing proportional operation, identifying current variation trend, and if it is less than proportional threshold MK diff1 Then, 1-point full-cycle differential operation is performed.
The embodiment of the invention has the beneficial effects that:
under the condition of CT trailing, the method can quickly and correctly judge the CT trailing according to different electrical characteristics of 2-point cosine difference, 1-point full-cycle difference and full-cycle Fourier, so that the failure protection time delay of the circuit breaker is returned, the failure duration time after the circuit breaker fails is shortened, and the influence on the system stability is reduced. The rapidness and the correctness of CT trailing identification are improved, and the time delay of circuit breaker failure protection is optimized.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
The method and system for optimizing breaker failure protection based on comprehensive difference according to the present invention are described in further detail below with reference to the accompanying drawings and the detailed description.
FIG. 1 is a flow chart of a comprehensive differential-based optimization method for circuit breaker failure protection according to the present invention;
FIG. 2 is a logic diagram of the comprehensive differential-based optimization method for circuit breaker failure protection according to the present invention;
FIG. 3 is a schematic diagram of the current situation when the CT tail occurs around 90 degrees of current according to the circuit breaker failure protection optimization method based on comprehensive difference;
FIG. 4 is a schematic diagram of the effect of the full-cycle Fourier algorithm when the CT trailing occurs near the current 90 degrees according to the circuit breaker failure protection optimization method based on the comprehensive difference;
FIG. 5 is a schematic diagram of the effect of a 2-point cosine difference algorithm when CT trailing occurs around current 90 degrees according to the comprehensive difference-based breaker failure protection optimization method;
FIG. 6 is a schematic diagram of the effect of a 1-point full-cycle difference algorithm when CT trailing occurs near current 90 degrees according to the comprehensive difference-based breaker failure protection optimization method;
FIG. 7 is a schematic diagram of the current situation when the CT tail occurs near the current zero crossing point according to the comprehensive difference-based breaker failure protection optimization method of the present invention;
FIG. 8 is a schematic diagram of the effect of a full-cycle Fourier algorithm when the CT tail occurs near the current zero crossing point according to the circuit breaker failure protection optimization method based on comprehensive difference;
FIG. 9 is a schematic diagram of the effect of a 2-point cosine difference algorithm when CT trailing occurs near a current zero crossing point according to the comprehensive difference-based breaker failure protection optimization method of the present invention;
fig. 10 is a schematic diagram of the effect of a 1-point full-cycle difference algorithm when the CT tail occurs near the current zero crossing point according to the circuit breaker failure protection optimization method based on comprehensive difference.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein can be arranged and designed in a wide variety of different configurations.
Some embodiments of the invention are described in detail below with reference to the accompanying drawings. The embodiments and features of the embodiments described below can be combined with each other without conflict.
Referring to fig. 1 to 10, in a first aspect, an embodiment of the present application provides a circuit breaker failure protection optimization method based on comprehensive difference, including:
s1, forming a logical OR of a cosine criterion and a whole-cycle criterion, and identifying the current as a CT trailing current if any action of the cosine criterion and the whole-cycle criterion is performed.
And S2, if the CT trailing current is identified, controlling the circuit breaker failure protection to return in a delayed mode without tripping.
With reference to the first aspect, this embodiment provides a first possible implementation manner of the first aspect, where in S1, the forming a logical or from the cosine criterion and the full-cycle criterion, and identifying that the current is a CT trailing current if any one of the cosine criterion and the full-cycle criterion is performed includes:
and if the cosine criterion acts, judging that the current is the CT trailing current when the breaker is switched off near the zero crossing point.
And if the whole-cycle criterion acts, judging that the current is the CT trailing current when the circuit breaker is disconnected nearby 90 degrees.
Fig. 8 to 10 show the simulation effect of three algorithms when the fault current is trailing near the zero crossing, and it can be seen from the graphs that in the initial stage of CT trailing, a transient rise stage occurs in the 2-point cosine difference, and no rise stage occurs in both the 1-point full-cycle difference and the full-cycle fourier.
Fig. 4 to fig. 6 show the fault current tailing at around 90 degrees, and the simulation effect of the three algorithms, as can be seen from the graphs, in the initial stage of CT tailing, a short rising stage occurs in a full-period fourier transform, and a rising stage does not occur in both a 1-point full-period difference and a 2-point cosine difference. In an alternating current power grid, a breaker can be selected to be opened near a zero crossing point, so that the occurrence probability of the situation is low, but the criterion is still set for the completeness of the criterion.
In order to ensure the correctness of the criterion, 2-3 points are generally selected to meet the criterion, identified as CT trailing and matched with a proportion threshold for use.
With reference to the first aspect, an embodiment of the present application provides a second possible implementation manner of the first aspect, where the cosine criterion calculation method includes:
and calculating a 2-point cosine difference proportion result, and when the circuit breaker near the current zero crossing point is switched off, the 2-point cosine difference is increased in short-time amplitude and is judged as the CT trailing current.
And calculating a 1-point full-cycle difference proportion result, and when the circuit breaker is switched off near the current 90 degrees or near a zero crossing point, the 1-point full-cycle difference does not have amplitude increase.
And forming a logical AND of the 2-point cosine differential proportion result and the 1-point full-cycle differential proportion result to form a cosine criterion, and identifying the CT trailing current when the circuit breaker is switched off near the current zero crossing point.
With reference to the first aspect, an embodiment of the present application provides a third possible implementation manner of the first aspect, where the method for calculating the weekly criterion includes:
and calculating a full-period Fourier proportion result, when the circuit breaker is disconnected near the current 90 degrees, the full-period Fourier generation short-time amplitude value is increased, and the current is judged to be CT trailing current.
And calculating a 1-point full-cycle difference proportion result, and when the circuit breaker is switched off near the current 90 degrees or near a zero crossing point, the 1-point full-cycle difference does not have amplitude increase.
And (3) forming a logical AND of the 1-point full-cycle differential proportion result and the full-cycle Fourier proportion result to form a full-cycle criterion, and identifying the CT trailing current when the circuit breaker is disconnected near the current 90 degrees.
In combination with the first aspect, the present examples provide a fourth possible implementation manner of the first aspect,
wherein, the calculation method of the whole-week Fourier proportion result comprises the following steps of calculating the calculation result of the current time of the whole-week Fourier
Calculating the pre-week calculation of full-week Fourier
According to the formula
Carrying out proportional operation, identifying the current variation trend, if the current variation trend is greater than a full-period Fourier proportion threshold, indicating that the current is the CT trailing current when the circuit breaker is disconnected, carrying out full-period Fourier action, wherein the value of the full-period Fourier proportion threshold is
The value of (c).
The full-cycle Fourier coefficient algorithm is as follows:
in the formula, N is the number of sampling points of a cycle, N is the sampling number of the cycle, yc is the real part coefficient, and ys is the imaginary part coefficient.
Calculation of the real and imaginary parts of the whole-cycle fourier:
in the formula, x k For the sample points, re is the real part and im is the imaginary part.
The calculation method of the 2-point cosine difference proportion result comprises the following steps of calculating the 2-point cosine difference calculation result of the current moment
Calculating 2-point cosine difference calculation result before current one circle
According to the formula
Carrying out proportional operation, identifying the current change trend, if the current change trend is greater than a 2-point cosine differential proportion threshold, indicating that the current is the CT trailing current when the circuit breaker is switched off, carrying out 2-point cosine differential action, wherein the value of the 2-point cosine differential proportion threshold is MK cos2 The value of (c).
The differential cosine coefficient algorithm of the 2-point cosine differential is as follows:
in the formula, dyc 2 And fusing the cosine coefficient after 2-point difference, wherein yc is a full-period Fourier real part coefficient.
The differential cosine coefficient vector dyc 2 Substituting into a mann-Morrison algorithm after sine correction, and concretely comprising the following steps:
in the formula, mc 2 Is the coefficient of the real part of the 2-point cosine difference, ms 2 Is a 2-point cosine difference imaginary coefficient.
The real and imaginary parts of the 2-point cosine difference are calculated as follows:
in the formula, x (k) is a sampling value, re2 is a 2-point cosine difference real part, and im2 is a 2-point cosine difference imaginary part.
The calculation method of the 1-point full-cycle difference proportion result comprises the steps of calculating the 1-point full-cycle difference calculation result of the current moment
Calculating the 1-point full-cycle difference calculation result before one cycle of current
According to the formula
Carrying out proportional operation, identifying the current variation trend, if the current variation trend is smaller than a 1-point full-cycle differential ratio threshold, carrying out 1-point full-cycle differential action, wherein the value of the 1-point full-cycle differential ratio threshold is MK diff1 The value of (c).
The difference coefficient algorithm of the 1-point full-cycle difference is as follows:
in the formula, yc is a full-period Fourier cosine coefficient, ys is a full-period Fourier sine coefficient, dyc1 is a cosine coefficient containing difference, and dys1 is a sine coefficient containing difference.
The real and imaginary parts of the 1-point difference full-perimeter Fourier are calculated as follows:
in the formula, x (k) is a sampling value, re1 is a real part of the full cycle of the 1-point difference, and im1 is an imaginary part of the full cycle of the 1-point difference.
Referring to fig. 1 to 10, in a second aspect, the present application further provides a circuit breaker failure protection optimization system based on comprehensive difference, which is used to implement the circuit breaker failure protection optimization method based on comprehensive difference as described above, and includes:
and the identification device is used for identifying the CT tail current when the breaker is opened near the current 90 degrees and near the current zero crossing point.
And the control device is used for controlling the circuit breaker failure protection to return in a delayed mode without tripping when the CT trailing current is identified.
With reference to the second aspect, embodiments of the present application provide a first possible implementation manner of the second aspect, where the identification apparatus includes:
and the 2-point cosine difference calculating module is used for calculating a 2-point cosine difference proportion result.
And the 1-point all-round difference calculating module is used for calculating a 1-point all-round difference proportion result.
And the whole-week Fourier calculation module is used for calculating a whole-week Fourier proportion result.
And the cosine criterion module is used for forming a logical AND of the 2-point cosine differential proportion result and the 1-point full-cycle differential proportion result to form a cosine criterion and identifying the CT trailing current when the circuit breaker is switched off near the current zero crossing point.
And the whole-cycle criterion module is used for forming a logical AND of the 1-point whole-cycle differential proportion result and the whole-cycle Fourier proportion result to form a whole-cycle criterion and identifying the CT trailing current when the circuit breaker is disconnected at a current of 90 degrees.
And the CT trailing current identification module is used for forming a logical OR by the cosine criterion and the full-period criterion, and identifying the CT trailing current by any action of the cosine criterion and the full-period criterion.
With reference to the second aspect, embodiments of the present application provide a second possible implementation manner of the second aspect, where the full-circle fourier computing module includes:
a whole-week Fourier current time calculating unit for calculating the current time calculation result of the whole-week Fourier
A complete Fourier one week previous calculation unit for calculating complete Fourier one week previous calculation result
A full-period Fourier proportion operation unit for calculating the ratio according to the formula
Carrying out proportional operation, identifying the current variation trend, and if the current variation trend is larger than a proportional threshold
A full-cycle fourier transform action.
With reference to the second aspect, an embodiment of the present application provides a third possible implementation manner of the second aspect, where the 2-point cosine difference calculating module includes:
a 2-point cosine difference current time calculation unit for calculating the current time calculation result of the 2-point cosine difference
A 2-point cosine difference one-cycle-before calculation unit for calculating 2-point cosine difference one-cycle-before calculation result
2-point cosine difference proportional operation unit for calculating the difference according to formula
Performing proportional operation, identifying current variation trend, and if it is greater than proportional threshold MK cos2 Then 2-point cosine differential action.
With reference to the second aspect, an embodiment of the present application provides a fourth possible implementation manner of the second aspect, where the 1-point full-cycle difference calculating module includes:
a 1-point all-round difference current time calculation unit for calculating the current time calculation result of the 1-point all-round difference
A 1-point all-round difference one-week-ahead calculation unit for calculating the 1-point all-round difference one-week-ahead calculation result
1 point full cycleA difference proportion operation unit for calculating the difference
Performing proportional operation, identifying current variation trend, and if it is less than proportional threshold MK diff1 Then, 1-point full-cycle differential operation is performed.
The embodiment of the invention aims to protect a breaker failure protection optimization method and system based on comprehensive difference, and the method and system have the following effects:
under the condition of CT trailing, the CT trailing is quickly and correctly judged according to different electrical characteristics of 2-point cosine difference, 1-point full-cycle difference and full-cycle Fourier, so that the failure protection time delay of the circuit breaker is returned, the failure duration time after the circuit breaker fails is shortened, and the influence on the system stability is reduced. The method improves the rapidity and the correctness of CT trailing identification, and optimizes the time delay of circuit breaker failure protection.
The computer program product of the comprehensive differential-based breaker failure protection optimization method and system provided by the embodiments of the present application includes a computer readable storage medium storing program codes, where instructions included in the program codes may be used to execute the methods in the foregoing method embodiments, and specific implementations may refer to the method embodiments, which are not described herein again.
Specifically, the storage medium can be a general storage medium, such as a mobile magnetic disk, a hard disk, and the like, and when a computer program on the storage medium is executed, the circuit breaker failure protection optimization method based on the comprehensive difference can be executed, so that CT trailing can be quickly and correctly determined, and the circuit breaker failure protection is delayed and returned.
The functions, if implemented in software functional units and sold or used as a stand-alone product, may be stored in a non-transitory computer-readable storage medium executable by a processor. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including 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: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present application, and are used to illustrate the technical solutions of the present application, but not to limit the technical solutions, and the scope of the present application is not limited to the above-mentioned embodiments, although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope disclosed in the present application; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present application and are intended to be covered by the appended claims. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (7)
1. A comprehensive difference-based breaker failure protection optimization method is characterized by comprising the following steps:
the cosine criterion and the full-period criterion are combined into a logical OR, and if any action of the cosine criterion and the full-period criterion is carried out, the current is identified as the CT trailing current;
if the CT trailing current is identified, controlling the circuit breaker failure protection to return in a delayed mode without tripping;
the cosine criterion calculation method comprises the following steps:
calculating a 2-point cosine difference proportion result, and judging that the amplitude of the 2-point cosine difference is increased in a short time when the circuit breaker near the current zero crossing point is switched off, so that the current is CT trailing current;
calculating a 1-point full-cycle difference proportion result, wherein when the circuit breaker is switched off near the current 90 degrees or near a zero crossing point, the amplitude of the 1-point full-cycle difference is not increased;
forming a logical AND by the 2-point cosine differential proportion result and the 1-point full-cycle differential proportion result to form a cosine criterion, and identifying the CT trailing current when the circuit breaker is switched off near the current zero crossing point;
the calculation method of the all-round criterion comprises the following steps:
calculating a full-period Fourier proportion result, and judging that the full-period Fourier generation short-time amplitude is increased when the circuit breaker is disconnected near the current 90 degrees, and the current is CT trailing current;
calculating a 1-point full-cycle difference proportion result, wherein when the circuit breaker is switched off near the current 90 degrees or near a zero crossing point, the 1-point full-cycle difference does not have amplitude increase;
and (3) forming a logical AND by the 1-point full-cycle difference proportion result and the full-cycle Fourier proportion result to form a full-cycle criterion, and identifying the CT trailing current when the circuit breaker is disconnected near the current 90 degrees.
2. The integrated differential-based breaker failure protection optimization method of claim 1, wherein the step of logically or-ing the cosine criterion and the full-cycle criterion, and if any one of the cosine criterion and the full-cycle criterion is operated, identifying the current as the CT trailing current comprises:
if the cosine criterion acts, the current is judged to be CT trailing current when the circuit breaker is switched off near the zero crossing point;
and if the whole-cycle criterion acts, judging that the current is the CT trailing current when the circuit breaker is disconnected nearby 90 degrees.
3. The comprehensive differential-based breaker failure protection optimization method according to claim 2, wherein the full-cycle Fourier proportion result is calculated by calculating the current time calculation result of the full-cycle Fourier
Calculating the pre-week calculation of full-week Fourier
According to the formula
Carrying out proportional operation, identifying the current change trend, if the current change trend is greater than a full-cycle Fourier proportional threshold, indicating that the current is CT trailing current when the breaker is disconnected, and carrying out full-cycle Fourier action;
the calculation method of the 2-point cosine difference proportion result comprises the steps of calculating the 2-point cosine difference calculation result of the current moment
Calculating 2-point cosine difference calculation result before current one circle
According to the formula
Carrying out proportional operation, identifying the current variation trend, if the current variation trend is greater than a 2-point cosine differential proportional threshold, indicating that the current is the CT trailing current when the circuit breaker is disconnected, and carrying out 2-point cosine differential action;
the calculation method of the 1-point full-cycle difference proportion result comprises the steps of calculating the 1-point full-cycle difference calculation result of the current at the current moment
Calculating the 1-point full-cycle difference calculation result before one cycle of current
According to the formula
And (4) carrying out proportional operation, identifying the current change trend, and carrying out 1-point full-cycle differential action if the current change trend is smaller than a 1-point full-cycle differential proportion threshold.
4. A comprehensive differential-based circuit breaker failure protection optimization system for implementing the comprehensive differential-based circuit breaker failure protection optimization method according to any one of claims 1 to 3, comprising:
the identification device is used for identifying that the current is CT trailing current, and forming a logical OR by a cosine criterion and a full-period criterion, wherein the current is CT trailing current if any action of the cosine criterion and the full-period criterion is performed;
the control device is used for controlling the circuit breaker failure protection time delay return without tripping when the CT trailing current is identified;
the identification device comprises:
the full-period Fourier calculation module is used for calculating a full-period Fourier proportion result, when the circuit breaker close to the current 90 degrees is disconnected, the short-time amplitude of the full-period Fourier is increased, and the current is judged to be CT trailing current;
the 2-point cosine difference calculating module is used for calculating a 2-point cosine difference proportional result, and when the circuit breaker near the current zero crossing point is switched off, the 2-point cosine difference is subjected to short-time amplitude increase and is judged as CT trailing current;
the 1-point full-cycle difference calculating module is used for calculating a 1-point full-cycle difference proportion result, and when the circuit breaker is switched off near the current 90 degrees or near a zero crossing point, the 1-point full-cycle difference does not have amplitude values increased;
the cosine criterion module is used for forming a logical AND of the 2-point cosine differential proportion result and the 1-point full-period differential proportion result to form a cosine criterion and identifying CT trailing current when the circuit breaker is switched off near a current zero crossing point;
and the whole-cycle criterion module is used for forming a logical AND of the 1-point whole-cycle differential proportion result and the whole-cycle Fourier proportion result to form a whole-cycle criterion and identifying the CT trailing current when the circuit breaker is disconnected at a current of 90 degrees.
5. The integrated differential-based breaker failure protection optimization system of claim 4, wherein the full-cycle Fourier calculation module comprises:
full Froude's current timeAn engraving calculation unit for calculating the current time calculation result of the whole-cycle Fourier
A week-before-full-Freund calculation unit for calculating the week-before-full-Freund calculation result
A full-period Fourier proportion operation unit for calculating the ratio according to the formula
And (4) carrying out proportional operation, identifying the current variation trend, and carrying out full-period Fourier action if the current variation trend is greater than the value of a full-period Fourier proportion threshold.
6. The integrated differential-based circuit breaker failure protection optimization system of claim 4, wherein the 2-point cosine differential calculation module comprises:
a 2-point cosine difference current time calculation unit for calculating the current time calculation result of the 2-point cosine difference
A 2-point cosine difference one-cycle-before calculation unit for calculating 2-point cosine difference one-cycle-before calculation result
2-point cosine difference proportional operation unit for calculating the difference according to formula
And (4) carrying out proportional operation, identifying the current change trend, and carrying out 2-point cosine differential action if the current change trend is greater than the value of the 2-point cosine differential proportion threshold.
7. The integrated differential-based circuit breaker failure protection optimization system of claim 4, wherein the 1-point full-cycle differential calculation module comprises:
a 1-point all-round difference current time calculation unit for calculating the current time calculation result of the 1-point all-round difference
A 1-point all-round difference one-week-ahead calculation unit for calculating the 1-point all-round difference one-week-ahead calculation result
A 1-point full-cycle differential proportional operation unit for calculating
And (4) carrying out proportional operation, identifying the current change trend, and carrying out 1-point full-cycle differential action if the current change trend is smaller than the value of the 1-point full-cycle differential proportion threshold.
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