CN106451369A - Current transformer tail current truncation method in failure protection - Google Patents
Current transformer tail current truncation method in failure protection Download PDFInfo
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- CN106451369A CN106451369A CN201510498385.3A CN201510498385A CN106451369A CN 106451369 A CN106451369 A CN 106451369A CN 201510498385 A CN201510498385 A CN 201510498385A CN 106451369 A CN106451369 A CN 106451369A
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Abstract
The invention relates to a current transformer tail current truncation method in failure protection. The method comprises the following steps that differential current of a sampling value is calculated; Fourier transform is performed on the differential current so as to determine the fundamental wave and the harmonic wave of the differential current; differential amplitude restoration is performed on the fundamental wave and differential amplitude restoration is not performed on the harmonic wave; CT tail current and short circuit current are determined according to the fundamental wave, the harmonic wave and amplitude restoration; and the criterion for CT tail current truncation is constructed according to the CT tail current and the short circuit current, and the braking coefficient of the criterion is corrected. According to the technical scheme, misoperation of failure protection is enabled not to perform under the condition of the CT tail current.
Description
Technical field：
The present invention relates to field of relay protection in power, it is more particularly to cutting in a kind of failure protection
Power-off current transformer tail currents method.
Background technology：
Breaker fail protection is a kind of back-up protection being widely applied in power system, is primarily directed to
Main protection correct operation exports, but guarantor when fault yet suffers from because breaker mechanism failure there is not tripping
Shield configuration.According to breaker fail protection principle, breaker fail protection time delay should be greater than chopper
Movement time and protection time of return sum.
Work as system jam, relay protection detects action outlet tripping operation after fault.After chopper disconnects,
CT current tail phenomenon due to there is the DC component of decay in current transformer (CT), now
CT electric current is not zero, but gradually decays to zero according to regular hour constant.
0.06A is generally adopted to be no flow setpoint in existing protection, this single threshold criterion is dragged to CT
The identification ability of tail current is poor.When there is CT tailing problem, and not to CT tail currents at
In the case of reason, protection time of return up to 200ms it is more likely that lead to failure protection misoperation thus
Expand fault coverage.
For problem above, the present invention proposes the chopping current transformer hangover electricity in a kind of failure protection
Stream method.
Content of the invention：
It is an object of the invention to provide a kind of chopping current transformer tail currents method in failure protection,
Guarantee that failure protection does not occur malfunction in the case of CT tail currents.
For achieving the above object, the present invention employs the following technical solutions：Electricity is blocked in a kind of failure protection
Current transformer tail currents method, comprises the following steps：
Calculate the difference current of sampled value；
Described difference current is carried out with Fourier's change and determines its fundamental wave harmonic；
By described fundamental wave carry out differential amplitude reduction and by described harmonic wave do not do difference amplitude reduction；
Reduced according to described fundamental wave, harmonic wave and amplitude and determine CT tail currents and short circuit current；
Build, according to described CT tail currents and short circuit current, the criterion blocking CT tail currents, and repair
The restraint coefficient of positive criterion.
Described difference currentDetermined by following formula：
Wherein,For n-th point sampling value electric current,For (n-1)th point sampling value electric current.
Described fundamental wave is obtained by half-wave Fourier transformation；Described harmonic wave is obtained by all-wave Fourier transformation
Arrive.
Fundamental wave is determined by half-wave Fourier transformation described in following formula：
In formula：N is periodic sampling points of fundamental signal；xkFor difference current kth time sampled value；a1T/2
It is the real part of fundametal compoment after half-wave Fourier transformation；b1T/2It is that fundamental wave divides after half-wave Fourier transformation
The imaginary part of amount；
Harmonic wave is determined by following formula all-wave Fourier transformation：
In formula：anTIt is the real part of nth harmonic component after all-wave Fourier transformation；bnTIt is through all-wave Fu
In after leaf transformation nth harmonic component imaginary part.
Determine that fundamental voltage amplitude reduces by following formula：
In formula：It is fourier transformed the phasor value obtaining for difference current；For being fourier transformed
And the phasor value obtaining after reducing；ω is fundamental signal angular frequency；T is fundamental signal cycle time.
Described tail currents pass through before current point half cycle according to window first through difference, by half-wave Fourier
Transformation calculations draw：
In formula：It is the fundamental current through half-wave Fourier transformation；For CT tail currents.
Described short circuit current by the previous cycle data window of the empty cycle of current point first through difference, by
All-wave Fourier transformation calculates：
In formula：It is the fundamental current through whole Fourier transformations；For short circuit current.
The harmonic wave of the described amplitude reduction not doing difference includes second harmonic and triple-frequency harmonics, described secondary humorous
Ripple and triple-frequency harmonics by current point previous cycle data window first through difference, become by all-wave Fourier
Change and calculate：
In formula：It is the second harmonic through all-wave Fourier transformation；It is through all-wave Fourier transformation
Triple-frequency harmonics；
The process that described structure blocks the criterion of CT tail currents includes：Set up rectangular coordinate system, with short
Road electric currentFor abscissa line, CT tail currentsFor coordinate longitudinal axis described point, formedBent
Line.
When chopper does not disconnect,Slope ≈ 1, the second harmonic of the sample rate current of calculating and three
Subharmonic numerical value is little；Chopper disconnects, and CT tail currents, calculates the all-wave Fourier of harmonic wave
Start across window, the harmonic wave of calculating increases suddenly, harmonic content is represented with second harmonic and triple-frequency harmonics sum：
CT tail currents block criterion：
In formula：K is restraint coefficient, K=0.5*IharmonicIf, Iharmonic＞ 1, K=0.5；Iset1=0.05A；
Iset1=0.3A.
When meeting above-mentioned criterion, block CT tail currents.
With immediate prior art ratio, the present invention provides technical scheme to have following excellent effect
1st, technical solution of the present invention is judged based on CT tail currents-short circuit current criterion plane,
In the case of there are CT tail currents, can quickly block CT tail currents, shorten protection time of return；
2nd, technical solution of the present invention is prevented effectively from existing protection because identifying that CT tail currents cause in time
The situation of failure protection malfunction；
3rd, the restraint coefficient of technical solution of the present invention correction criterion, improves the sensitivity of criterion.
Brief description
Fig. 1 is the criterion floor map blocking CT tail currents of the embodiment of the present invention；
Fig. 2 is CT tail currents and the calculation of short-circuit current schematic diagram of the embodiment of the present invention；
Fig. 3 is the current sampling data waveform diagram of the embodiment of the present invention；
Fig. 4 is the CT tail currents of the embodiment of the present invention and short circuit current described point in criterion plane draws
Curve synoptic diagram；
Fig. 5 is the embodiment of the present inventionChange over curve synoptic diagram.
Specific embodiment
With reference to embodiment, the invention will be described in further detail.
Embodiment 1：
The invention of this example provides a kind of chopping current transformer tail currents method in failure protection, including
Following steps：
(1) difference current：Protection installation place sample rate current beCalculate difference current
(2) Fourier transformation：Half-wave Fourier algorithms fundamental wave formula：
In formula：N is periodic sampling points of fundamental signal；xkFor difference current kth time sampled value；a1T/2
It is the real part of fundametal compoment after half-wave Fourier transformation；b1T/2It is that fundamental wave divides after half-wave Fourier transformation
The imaginary part of amount.
All-wave Fourier algorithm formula：
In formula：anTIt is the real part of nth harmonic (n=1 is fundamental wave) component after all-wave Fourier transformation；
bnTIt is the imaginary part of nth harmonic (n=1 is fundamental wave) component after all-wave Fourier transformation.
(3) differential amplitude reduction：Difference current reduces formula after being fourier transformed
In formula：It is fourier transformed the phasor value obtaining for difference current；For being fourier transformed
And the phasor value obtaining after reducing.
(4) CT tail currents and short circuit current：Before current point half cycle according to window first through difference, after
Calculate CT tail currents through half-wave Fourier transformation：
In formula：It is the fundamental current through half-wave Fourier transformation；For CT tail currents.
The previous cycle data window of the empty cycle of current point first through difference, by all-wave Fourier transformation meter
Calculation draws short circuit current：
In formula：It is the fundamental current through whole Fourier transformations；For short circuit current.As Fig. 2
Shown.
(5) current point previous cycle data window, first through difference, calculates by all-wave Fourier transformation
Go out second harmonic and triple-frequency harmonics (calculating the amplitude reduction that all harmonic waves do not do difference)：
In formula：It is the second harmonic through all-wave Fourier transformation；It is through all-wave Fourier transformation
Triple-frequency harmonics.
Set up rectangular coordinate system, with short circuit currentFor abscissa line, CT tail currentsFor coordinate
Longitudinal axis described point, formsCurve.
When chopper does not disconnect,Slope ≈ 1, calculate sample rate current second harmonic, three times
Harmonic wave numerical value is little；Chopper disconnects, and CT tail currents, and the all-wave Fourier calculating harmonic wave opens
Begin across window, the harmonic wave of calculating increases suddenly, harmonic content is represented with second harmonic and triple-frequency harmonics sum：
CT tail currents block criterion：
In formula：K is restraint coefficient, K=0.5*IharmonicIf, Iharmonic＞ 1, K=0.5；Iset1=0.05A；
Iset1=0.3A.
When meeting above-mentioned criterion, block CT tail currents.
, as shown in figure 3, the chopper disconnection as t=55ms, CT hangover electricity in current sampling data waveform
Stream.
Calculate CT tail currents and short circuit current, and described point draws in criterion planeCurve,
As shown in Figure 4.Calculate second harmonic and third-harmonic component sum IharmonicChange over curve, such as scheme
Shown in 5.
When switch closes,The slope of curve is approximately 1, second harmonic now,
Triple-frequency harmonics is little.Switch off and CT tail currents occur, the all-wave Fourier transformation meter of this time-harmonic wave
Calculate result and start across window, the harmonic wave of calculating increases suddenly, and criterion restraint coefficient K is with harmonic content IharmonicChange
Change and change.Curve the 13rd point (10.83ms) after switching off falls into areism.
As shown in figure 3, it is 0.06A that existing Protection criteria no flows threshold value, there are CT tail currents
In the case of, protection time of return is more than 100ms, and the criterion in the present invention can be cut in 10.83ms
Disconnected CT tail currents, substantially reduce protection time of return, improve the reliability of failure protection.
Finally it should be noted that：Above example is only in order to illustrate technical scheme rather than to it
Limit, although those of ordinary skill in the art should be understood with reference to above-described embodiment：Still can be right
The specific embodiment of the present invention is modified or equivalent, and these are without departing from present invention spirit and model
Any modification enclosed or equivalent, all apply for the pending present invention claims it
Interior.
Claims (9)
1. a kind of chopping current transformer tail currents method in failure protection it is characterised in that：Comprise the following steps：
Calculate the difference current of sampled value；
Described difference current is carried out with Fourier's change and determines its fundamental wave harmonic；
By described fundamental wave carry out differential amplitude reduction and by described harmonic wave do not do difference amplitude reduction；
Reduced according to described fundamental wave, harmonic wave and amplitude and determine CT tail currents and short circuit current；
Build, according to described CT tail currents and short circuit current, the criterion blocking CT tail currents, and revise the restraint coefficient of criterion.
2. as claimed in claim 1 a kind of chopping current transformer tail currents method in failure protection it is characterised in that：Described difference currentDetermined by following formula：
Wherein,For n-th point sampling value electric current,For (n-1)th point sampling value electric current.
3. as claimed in claim 1 a kind of chopping current transformer tail currents method in failure protection it is characterised in that：Described fundamental wave is obtained by half-wave Fourier transformation；Described harmonic wave is obtained by all-wave Fourier transformation.
4. as claimed in claim 3 a kind of chopping current transformer tail currents method in failure protection it is characterised in that：Fundamental wave is determined by half-wave Fourier transformation described in following formula：
In formula：N is periodic sampling points of fundamental signal；xkFor difference current kth time sampled value；a1T/2It is the real part of fundametal compoment after half-wave Fourier transformation；b1T/2It is the imaginary part of fundametal compoment after half-wave Fourier transformation；
Harmonic wave is determined by following formula all-wave Fourier transformation：
In formula：anTIt is the real part of nth harmonic component after all-wave Fourier transformation；bnTIt is the imaginary part of nth harmonic component after all-wave Fourier transformation.
5. as claimed in claim 1 a kind of chopping current transformer tail currents method in failure protection it is characterised in that：Determine that fundamental voltage amplitude reduces by following formula：
In formula：It is fourier transformed the phasor value obtaining for difference current；For the phasor value being fourier transformed and obtain after reducing；ω is fundamental signal angular frequency；T is fundamental signal cycle time.
6. as claimed in claim 4 a kind of chopping current transformer tail currents method in failure protection it is characterised in that：Described tail currents pass through before current point half cycle according to window first through difference, calculate by half-wave Fourier transformation：
In formula：It is the fundamental current through half-wave Fourier transformation；For CT tail currents.
7. as claimed in claim 5 a kind of chopping current transformer tail currents method in failure protection it is characterised in that：Described short circuit current, is calculated first through difference by all-wave Fourier transformation by the previous cycle data window of the empty cycle of current point：
In formula：It is the fundamental current through whole Fourier transformations；For short circuit current.
8. as claimed in claim 7 a kind of chopping current transformer tail currents method in failure protection it is characterised in that：The harmonic wave of the described amplitude reduction not doing difference includes second harmonic and triple-frequency harmonics, described second harmonic and triple-frequency harmonics by current point previous cycle data window first through difference, calculate by all-wave Fourier transformation：
In formula：It is the second harmonic through all-wave Fourier transformation；It is the triple-frequency harmonics through all-wave Fourier transformation.
9. as claimed in claim 8 a kind of chopping current transformer tail currents method in failure protection it is characterised in that：The process that described structure blocks the criterion of CT tail currents includes：Set up rectangular coordinate system, with short circuit currentFor abscissa line, CT tail currentsFor coordinate longitudinal axis described point, formedCurve.
When chopper does not disconnect,Slope ≈ 1；When chopper disconnects, CT tail currents occur, the all-wave Fourier calculating harmonic wave starts across window, and the harmonic wave of calculating increases suddenly, harmonic content is represented with second harmonic and triple-frequency harmonics sum：
CT tail currents block criterion：
In formula：K is restraint coefficient, K=0.5*IharmonicIf, Iharmonic＞ 1, K=0.5；Iset1=0.05A；Iset1=0.3A.
When meeting above-mentioned criterion, block CT tail currents.
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| CN201510498385.3A CN106451369B (en) | 2015-08-13 | 2015-08-13 | A kind of chopping current mutual inductor tail currents method in failure protection |
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| CN201510498385.3A CN106451369B (en) | 2015-08-13 | 2015-08-13 | A kind of chopping current mutual inductor tail currents method in failure protection |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107134763A (en) * | 2017-07-13 | 2017-09-05 | 积成软件有限公司 | The method of discrimination that a kind of fault trip is quickly returned |
| CN108631258A (en) * | 2018-05-18 | 2018-10-09 | 许继集团有限公司 | Breaker failure method of discrimination based on fourier algorithm, control method and device |
| CN111797699A (en) * | 2020-06-10 | 2020-10-20 | 积成软件有限公司 | Method for identifying fault-removal CT trailing waveform |
| CN112462179A (en) * | 2020-11-17 | 2021-03-09 | 中船动力研究院有限公司 | Narrow band-pass filtering method, device, equipment and storage medium |
| WO2021047568A1 (en) * | 2019-09-11 | 2021-03-18 | 国电南瑞科技股份有限公司 | Method for automatically adjusting malfunction protection delay by means of tail current identification |
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| US6829544B1 (en) * | 2000-04-10 | 2004-12-07 | General Electric Company | Line current differential protective relaying method and relay for in-zone tapped transformers |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107134763A (en) * | 2017-07-13 | 2017-09-05 | 积成软件有限公司 | The method of discrimination that a kind of fault trip is quickly returned |
| CN108631258A (en) * | 2018-05-18 | 2018-10-09 | 许继集团有限公司 | Breaker failure method of discrimination based on fourier algorithm, control method and device |
| WO2021047568A1 (en) * | 2019-09-11 | 2021-03-18 | 国电南瑞科技股份有限公司 | Method for automatically adjusting malfunction protection delay by means of tail current identification |
| CN111797699A (en) * | 2020-06-10 | 2020-10-20 | 积成软件有限公司 | Method for identifying fault-removal CT trailing waveform |
| CN112462179A (en) * | 2020-11-17 | 2021-03-09 | 中船动力研究院有限公司 | Narrow band-pass filtering method, device, equipment and storage medium |
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