CN101764391A - Method and system for braking magnetizing inrush current in differential protection of ultra-high voltage transformer - Google Patents
Method and system for braking magnetizing inrush current in differential protection of ultra-high voltage transformer Download PDFInfo
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Abstract
The invention provides a method for braking a magnetizing inrush current in the differential protection of an ultra-high voltage transformer, which comprises the following steps: acquiring a corresponding magnetizing inrush current criterion of each phase by the weight of an amplitude bias current, the weight of a secondary harmonic current and a symmetry degree of the waveform of each phase; and braking the magnetizing inrush currents of the phases whose magnetizing inrush current criterions are greater than a magnetizing inrush current braking coefficient. The method provided by the invention comprehensively considers the sizes of the three parameters, i.e. the weight of the amplitude bias current, the weight of the secondary harmonic current and the symmetry degree of the waveform. The increase or decrease of only one of the parameters cannot determine whether the whole magnetizing inrush current criterion is greater than or less than the magnetizing inrush current braking coefficient so as to solve the defect of only utilizing the secondary harmonic as the magnetizing inrush current criterion in the prior art. The invention makes the braking of the magnetizing inrush current more reliable so as to have a more accurate tripping of the differential protection of the transformer without causing false tripping or refuse operation. The invention also provides a system for braking the magnetizing inrush current in the differential protection of the ultra-high voltage transformer.
Description
Technical field
The present invention relates to the extra-high voltage transformer technical field, the method and system of braking magnetizing inrush current in particularly a kind of differential protection of ultra-high voltage transformer.
Background technology
At present, the differential protection of transformer mainly solves two problems in practice: the one, differentiate magnetizing inrush current and fault current; The 2nd, distinguish external fault and internal fault.The differential protection of transformer can be distinguished external fault and internal fault to a certain extent preferably, but also comes with some shortcomings in the identification of magnetizing inrush current and fault current.
At present, main by the main foundation of identification current waveform as judgement magnetizing inrush current and fault current.In various braking magnetizing inrush current schemes, secondary harmonic brake is relatively ripe and reliable.This method of discrimination is substantially all disposed in the protection of main transformer both at home and abroad.
Secondary harmonic brake mainly is divided into two kinds, is respectively " phase-splitting braking " and " or door braking ".
Described " phase-splitting braking " is specially: the second harmonic content of transformer one phase surpasses at 15% o'clock, only brakes this phase.
Described " or door braking " is specially: the second harmonic content of the arbitrary phase of transformer surpasses at 15% o'clock, the braking three-phase.
But all there is defective in these two kinds of modes of braking at present.
" phase-splitting braking " may cause differential protection malfunction.Magnetizing inrush current was subjected to the influence of switching angle, transformer remanent magnetism and system side when for example the transformer sky filled, and the second harmonic content size of each phase is inequality.Operating experience for many years shows that with test may to have a certain second harmonic content mutually lower, therefore adopts the phase-splitting braking to cause differential protection malfunction easily.
" or door braking " may cause differential protection tripping or deferred action.For example, Transformer Close when inner single-phase fault, A phase fault for example; B is non-fault phase with C mutually mutually, and may there be magnetizing inrush current in the B phase mutually with C, and its second harmonic content is higher, owing to adopt or the door braking, therefore, meeting locking rate of three phase flow is differential, and at this moment, fault phase A also can't export mutually.In addition, if internal fault because of a variety of causes, when causing certain phase second harmonic content higher, may cause the differential protection tripping.For example the saturated harmonic wave that will cause of current transformer CT produces, and also can there be harmonic wave in system during fault.
In sum, it still is that " or door braking " all exists defective that the secondary harmonic brake of present magnetizing inrush current adopts " phase-splitting braking ", causes the malfunction and the tripping of transformer differential protection protection easily.
Summary of the invention
The technical problem to be solved in the present invention provides the method and system of braking magnetizing inrush current in a kind of differential protection of ultra-high voltage transformer, and transformer differential protection is moved accurately and reliably.
The invention provides the method for braking magnetizing inrush current in the differential protection of ultra-high voltage transformer, comprising:
Obtain every corresponding magnetizing inrush current criterion by the weight of the amplitude bias current of every phase, the weight and the waveform symmetry degree of second harmonic current;
With the braking magnetizing inrush current of described magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient.
Preferably, the weight of described amplitude bias current by every phase, the weight and the waveform symmetry degree of second harmonic current obtain every corresponding magnetizing inrush current criterion; Be specially: f (k
0, k
2, D)=C
1k
0+ C
2k
2+ C
3D; k
0Be the weight of described amplitude bias current, k
2Be the weight of described second harmonic current, D is described waveform symmetry degree; C
1, C
2, C
3Be characteristic coefficient.
Preferably, described C
1, C
2, C
3Characteristic coefficient is specially:
C
1＝0.8×I
2/I
1；
C
3＝0.1；
Wherein, I
0Expression amplitude bias current; I
1The expression fundamental current; I
2The expression second harmonic current; I
eThe rated current of indication transformer.
Preferably, the scope of described braking magnetizing inrush current coefficient is 0.15-0.20.
Preferably, after the braking magnetizing inrush current of described magnetizing inrush current criterion, also comprise: this phase of locking differential protection greater than the phase of braking magnetizing inrush current coefficient.
Preferably, the weight of described amplitude bias current is: the ratio of amplitude bias current and fundamental current.
Preferably, the weight of described second harmonic current is respectively: the ratio of second harmonic current and fundamental current.
The present invention also provides the system of braking magnetizing inrush current in a kind of differential protection of ultra-high voltage transformer, comprising: computing unit, judging unit, transmitting element and brake unit;
Described computing unit is used for calculating every corresponding magnetizing inrush current criterion by the weight of the amplitude bias current of every phase, the weight and the waveform symmetry degree of second harmonic current;
Judging unit is used to judge that whether the described magnetizing inrush current criterion of described computing unit calculating is greater than the braking magnetizing inrush current coefficient;
Described transmitting element is used for sending brake signal to described brake unit when the described magnetizing inrush current criterion of described judgment unit judges during greater than the braking magnetizing inrush current coefficient;
Described brake unit is used to brake the magnetizing inrush current of magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient.
Preferably, described computing unit is used for calculating every corresponding magnetizing inrush current criterion by the weight of the amplitude bias current of every phase, the weight and the waveform symmetry degree of second harmonic current; Concrete by following formula realization:
F (k
0, k
2, D)=C
1k
0+ C
2k
2+ C
3D; k
0Be the weight of described amplitude bias current, k
2Be the weight of described second harmonic current, D is described waveform symmetry degree; C
1, C
2, C
3Be characteristic coefficient.
Preferably, also comprise locking unit, after described brake unit is with the braking magnetizing inrush current of magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient, be used for the differential protection of this phase of locking.
Compared with prior art, the present invention has the following advantages:
The method and system of braking magnetizing inrush current in the differential protection of ultra-high voltage transformer provided by the invention, the magnetizing inrush current criterion that provides have been taken all factors into consideration the weight of the amplitude bias current of each phase current, the weight of second harmonic current and the size of waveform symmetry degree.When transformer has internal fault, for the fault phase: because the weight of second harmonic current goes to zero, symmetry also goes to zero; the weight of amplitude bias current is less, and therefore, the magnetizing inrush current criterion is less than the braking magnetizing inrush current coefficient; this phase differential protection can action message by opening.When the transformer sky fills in internal fault, mutually above-mentioned identical situation is arranged also for fault, this phase differential protection can action message by opening.More than two kinds of situations can guarantee that differential protection moves accurately and reliably, avoid tripping.When the transformer sky filled, because the waveform that various factorss such as remanent magnetism, switching angle cause is comparatively symmetrical, promptly symmetry went to zero; But the weight of the weight of second harmonic current and amplitude bias current is bigger, and at this moment, the magnetizing inrush current criterion is greater than the braking magnetizing inrush current coefficient, this phase of locking differential protection, thus guarantee that differential protection malfunction can not occur.
Description of drawings
Fig. 1 is the typical magnetizing inrush current waveform of transformer;
Fig. 2 is the inventive method first embodiment flow chart;
Fig. 3 is the inventive method second embodiment flow chart;
Fig. 4 is the building-block of logic of braking magnetizing inrush current of the present invention;
Fig. 5 is the first example structure figure of system of the present invention;
Fig. 6 is the second example structure figure of system of the present invention.
Embodiment
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the specific embodiment of the present invention is described in detail below in conjunction with accompanying drawing.
In order to make those skilled in the art implement the present invention better, at first introduce several basic conceptions.
Referring to Fig. 1, this figure is the typical magnetizing inrush current waveform of transformer.
As can be seen from Figure 1 several characteristic amount: amplitude biasing, harmonic wave and waveform are interrupted.
Wherein, amplitude biasing can be found out by the negative semiaxis that waveform major part among Fig. 1 is positioned at the longitudinal axis, rather than evenly distribute at positive and negative semiaxis.Harmonic wave can find out that desirable crest should be an arc from the crest of waveform, seamlessly transits, and the broken line that the appearance of present crest is scabbled, this is mainly caused by harmonic wave.The waveform interruption is also caused by harmonic wave, causes waveform not seamlessly transit, but broken line occurs.
In the prior art only with the second harmonic of each phase criterion as each phase braking magnetizing inrush current, easy like this malfunction and the tripping that causes transformer differential protection, and comprehensive considering various effects of the present invention is as the criterion of braking magnetizing inrush current.
Referring to Fig. 2, this figure is the inventive method first embodiment flow chart.
S201: obtain every corresponding magnetizing inrush current criterion by the weight of the amplitude bias current of every phase, the weight and the waveform symmetry degree of second harmonic current.
Introduce the computational process of magnetizing inrush current criterion below in detail.
With I
0Expression amplitude bias current; I
1The expression fundamental current; I
2The expression second harmonic current.
Data window by 20ms adopts Fu Shi filtering can obtain the size of amplitude biasing and the size of second harmonic.
The weight of amplitude bias current is:
The weight of second harmonic is:
The waveform symmetry degree is represented with D.
If difference conductance number is I (k), sampling number weekly is the 2n point, to ordered series of numbers:
X(k)＝|I(k)+I(k+n)|/(|I(k)|+|I(k+n)|)，k＝1，2...n
Can think that X (k) is more little, it is many more that this puts contained fault message, and promptly the confidence level of fault is big more; Otherwise X (k) is big more, and the information of shoving that this point is comprised is many more, and the confidence level of promptly shoving is big more.Get a membership function, be made as A[X (k)], the information of comprehensive one-period, to k=1,2...n, try to achieve symmetry D and be:
Calculate every magnetizing inrush current criterion mutually by the weight of above-mentioned every phase amplitude bias current, the weight and the waveform symmetry degree of second harmonic.
S202: with the braking magnetizing inrush current of described magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient.
Whether the magnetizing inrush current criterion of judging every phase is greater than the braking magnetizing inrush current coefficient, with the braking magnetizing inrush current of magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient.For example, the magnetizing inrush current criterion of A phase is greater than the braking magnetizing inrush current coefficient, then with A phase braking magnetizing inrush current.
The method of braking magnetizing inrush current in the differential protection of ultra-high voltage transformer provided by the invention, the magnetizing inrush current criterion that provides have been taken all factors into consideration the weight of the amplitude bias current of each phase current, the weight of second harmonic current and the size of waveform symmetry degree.When transformer has internal fault, for the fault phase: because the weight of second harmonic current goes to zero, symmetry also goes to zero; the weight of amplitude bias current is less; therefore, the magnetizing inrush current criterion is less than the braking magnetizing inrush current coefficient, and this phase differential protection can action message.When the transformer sky fills in internal fault, mutually above-mentioned identical situation is arranged also for fault, this phase differential protection can action message.More than two kinds of situations can guarantee that differential protection moves accurately and reliably, avoid tripping.When the transformer sky filled, because the waveform that various factorss such as remanent magnetism, switching angle cause is comparatively symmetrical, promptly symmetry went to zero; But the weight of the weight of second harmonic current and amplitude bias current is bigger, and at this moment, the magnetizing inrush current criterion is greater than the braking magnetizing inrush current coefficient, this phase of locking differential protection, thus guarantee that differential protection malfunction can not occur.
Referring to Fig. 3, this figure is the inventive method second embodiment flow chart.
S301: calculate the electric current of each phase, comprise amplitude bias current I
0, fundamental current I
1With second harmonic current I
2
S302: the weight k that calculates the amplitude bias current by above-mentioned each electric current
0, second harmonic current weight k
2With waveform symmetry degree D.
S303: the magnetizing inrush current criterion f (k that calculates each phase
0, k
n, D).
To function of every phase structure:
f(k
0，k
2，D)＝C
1k
0+C
2k
2+C
3D (1)
Wherein, C
1, C
2, C
3Be characteristic coefficient.
Need to prove that C1 and second harmonic current are directly proportional with the ratio of fundamental current, scope is (0.8-0.9) I
2/ I
1The span of C2C3 is 0.1-0.2.
The preferred C of present embodiment
1, C
2, C
3Value as follows:
C
1＝0.8×I
2/I
1
C
3＝0.1
I
eThe rated current of indication transformer.
S304: whether the magnetizing inrush current criterion of judging the A phase if not, carries out S305 greater than the braking magnetizing inrush current coefficient; If carry out S306.
Promptly judge f
A(k
0, k
3, D)＞ε
ZdWhether set up,, illustrate that then there is magnetizing inrush current mutually in A, this phase of locking this moment differential protection if set up; If be false, then open this phase differential protection.
ε wherein
ZdBe the braking magnetizing inrush current coefficient, get 0.15～0.20 usually.In the present embodiment preferred 0.15.
S305: remove the locking of A phase magnetizing inrush current.
S306: put the locking of A phase magnetizing inrush current.
S307: whether the magnetizing inrush current criterion of judging the B phase if not, carries out S308 greater than the braking magnetizing inrush current coefficient; If carry out S309.
Promptly judge f
B(k
0, k
2, D)＞ε
ZdWhether set up.
S308: remove the locking of B phase magnetizing inrush current.
S309: put the locking of B phase magnetizing inrush current.
S310: whether the magnetizing inrush current criterion of judging the C phase if not, carries out S310 greater than the braking magnetizing inrush current coefficient; If carry out S312.
Promptly judge f
C(k
0, k
2, D)＞ε
ZdWhether set up.
S311: remove the locking of C phase magnetizing inrush current.
S312: put the locking of C phase magnetizing inrush current.
Need to prove, above-mentioned S304, S307 and S310 judge respectively A mutually, B mutually with C magnetizing inrush current criterion mutually whether greater than the braking magnetizing inrush current coefficient, the not free order of these three steps can be carried out simultaneously.
The transformer differential protection of using braking magnetizing inrush current method provided by the invention is described below in conjunction with Fig. 4.
Referring to Fig. 4, this figure is the building-block of logic based on braking magnetizing inrush current of the present invention.
In order to narrate conveniently order below:
Work as f
A(k
0, k
2, D)＞ε
ZdThe time be Fa; Work as f
A(k
0, k
2, D)≤ε
ZdThe time be Fa;
Work as f
B(k
0, k
2, D)＞ε
ZdThe time be Fb; Work as f
B(k
0, k
2, D)≤ε
ZdThe time be Fb;
Work as f
C(k
0, k
2, D)＞ε
ZdThe time be Fc; Work as f
C(k
0, k
2, D)≤ε
ZdThe time be Fc;
Make that the differential action of A phase ratio is A; The differential action of B phase ratio is B; The differential action of C phase ratio is C.
Make the transformer differential protection tripping operation be T.
Represent logical relation shown in Figure 4 with the mathematical logic formula below.
T＝AFa+BFb+CFc
Y1, Y2 and Y3 be three with door, wherein Y1 be the differential action of A phase ratio with Fa with.Promptly work as the differential action of A phase ratio, and f
A(k
0, k
2, D)≤ε
ZdThe time, Y1 is output as 1.
If f
A(k
0, k
2, D)＞ε
ZdIllustrate that then there is magnetizing inrush current mutually in A, this phase of locking this moment differential protection; Even the action of A phase ratio differential protection, transformer differential protection does not trip yet.
Y2 be the differential action of B phase ratio with Fb with.Promptly work as the differential action of B phase ratio, and f
B(k
0, k
2, D)≤ε
ZdThe time, Y2 is output as 1.
Y3 be the differential action of C phase ratio with Fc with.Promptly work as the differential action of C phase ratio, and f
C(k
0, k
2, D)≤ε
ZdThe time, Y3 is output as 1.
H be one or, promptly the output of three of Y1, Y2 and Y3 and door is as the input of H or door, when having at least one to be 1 among Y1, Y2 and the Y3, H is output as 1, at this moment, transformer differential protection tripping operation, i.e. T=1.
When transformer has internal fault, for the fault phase, because k
n→ 0, D → 0, k
0Less, therefore as can be known: f (k
0, k
2, D)＜ε
Zd, the reliable and action rapidly of protection.When transformer has internal fault, biased differential protection action, A phase fault for example, the differential action of A phase ratio, f
A(k
0, k
2, D)＜ε
Zd, so Y1 and door be output as 1, T is 1, i.e. transformer differential protection tripping operation.
When sky fills in internal fault,, k is arranged for the fault phase
n→ 0, D → 0, k
0Less, therefore as can be known: f (k
0, k
2, D)＜ε
Zd, the reliable and action rapidly of protection.
When sky fills, because the waveform that various factors such as remanent magnetism, switching angle cause symmetry comparatively, i.e. D → 0, but k
n, k
0Bigger, f (k
0, k
2, D)＞ε
Zd, protection reliably is failure to actuate.
Method provided by the invention has been taken all factors into consideration k
2, k
0Size cases with three parameters of D, only one of them parameter become big or the limit little, can not determine that whole magnetizing inrush current criterion is greater than the braking magnetizing inrush current coefficient or less than the braking magnetizing inrush current coefficient, has solved like this and has only utilized the drawback of second harmonic as the magnetizing inrush current criterion in the prior art.The present invention makes braking magnetizing inrush current more reliable, and then is that the transformer differential protection tripping operation is more accurate, can not cause malfunction or tripping.
Obviously, than only adopting k
2Prior art, this programme has higher reliability.
The method of braking magnetizing inrush current in the differential protection of ultra-high voltage transformer that provides based on the invention described above; the present invention also provides the system of braking magnetizing inrush current in a kind of differential protection of ultra-high voltage transformer provided by the invention, describes in detail below in conjunction with specific embodiment.
Referring to Fig. 5, this figure is based on the first example structure figure of system of the present invention.
The braking system of magnetizing inrush current comprises in the differential protection of ultra-high voltage transformer: computing unit 501, judging unit 502, transmitting element 503 and brake unit 504.
Described computing unit 501 is used for calculating every corresponding magnetizing inrush current criterion by the weight of the amplitude bias current of every phase, the weight and the waveform symmetry degree of second harmonic current;
Described computing unit 501, specifically calculate every corresponding magnetizing inrush current criterion by following formula:
f(k
0，k
2，D)＝C
1k
0+C
2k
2+C
3D；
Wherein, C
1, C
2, C
3Be characteristic coefficient; Preferred each value of present embodiment is as follows:
C
1＝0.8×I
2/I
1
C
3＝0.1
k
0Be the weight of described amplitude bias current, k
2Be the weight of described second harmonic current, D is described waveform symmetry degree.
Judging unit 502 is used to judge that whether the described magnetizing inrush current criterion of described computing unit 501 calculating is greater than the braking magnetizing inrush current coefficient;
Described transmitting element 503 is used for sending brake signal to described brake unit 504 when described judging unit 502 is judged described magnetizing inrush current criterion greater than the braking magnetizing inrush current coefficient.
Described brake unit 504 is used to brake the magnetizing inrush current of magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient.
The system of braking magnetizing inrush current in the differential protection of ultra-high voltage transformer provided by the invention, the magnetizing inrush current criterion that provides have taken all factors into consideration the weight of the amplitude bias current of each phase current, the weight of second harmonic current and the size of waveform symmetry degree.When transformer has internal fault, for the fault phase: because the weight of second harmonic current goes to zero, symmetry also goes to zero; the weight of amplitude bias current is less; therefore, the magnetizing inrush current criterion is less than the braking magnetizing inrush current coefficient, and this phase differential protection can action message.When the transformer sky fills in internal fault, mutually above-mentioned identical situation is arranged also for fault, this phase differential protection can action message.More than two kinds of situations can guarantee that differential protection moves accurately and reliably, avoid tripping.When the transformer sky filled, because the waveform that various factorss such as remanent magnetism, switching angle cause is comparatively symmetrical, promptly symmetry went to zero; But the weight of the weight of second harmonic current and amplitude bias current is bigger, and at this moment, the magnetizing inrush current criterion is greater than the braking magnetizing inrush current coefficient, this phase of locking differential protection, thus guarantee that differential protection malfunction can not occur.
Referring to Fig. 6, this figure is the second example structure figure of system of the present invention.
The difference of present embodiment and first embodiment of system is to have increased locking unit.
Locking unit 601 after described brake unit is with the braking magnetizing inrush current of magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient, is used for the differential protection of this phase of locking.
The above only is preferred embodiment of the present invention, is not the present invention is done any pro forma restriction.Though the present invention discloses as above with preferred embodiment, yet be not in order to limit the present invention.Any those of ordinary skill in the art, do not breaking away under the technical solution of the present invention scope situation, all can utilize the method and the technology contents of above-mentioned announcement that technical solution of the present invention is made many possible changes and modification, or be revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not break away from technical solution of the present invention, all still belongs in the scope of technical solution of the present invention protection any simple modification, equivalent variations and modification that above embodiment did according to technical spirit of the present invention.
Claims (10)
1. the method for braking magnetizing inrush current in the differential protection of ultra-high voltage transformer is characterized in that, comprising:
Obtain every corresponding magnetizing inrush current criterion by the weight of the amplitude bias current of every phase, the weight and the waveform symmetry degree of second harmonic current;
With the braking magnetizing inrush current of described magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient.
2. method according to claim 1 is characterized in that, the weight of described amplitude bias current by every phase, the weight and the waveform symmetry degree of second harmonic current obtain every corresponding magnetizing inrush current criterion; Be specially: f (k
0, k
2, D)=C
1k
0+ C
2k
2+ C
3D; k
0Be the weight of described amplitude bias current, k
2Be the weight of described second harmonic current, D is described waveform symmetry degree; C
1, C
2, C
3Be characteristic coefficient.
3. method according to claim 2 is characterized in that, described C
1, C
2, C
3Characteristic coefficient is specially:
C
1＝0.8×I
2/I
1；
C
3＝0.1；
Wherein, I
0Expression amplitude bias current; I
1The expression fundamental current; I
2The expression second harmonic current; I
eThe rated current of indication transformer.
4. method according to claim 1 is characterized in that, the scope of described braking magnetizing inrush current coefficient is 0.15-0.20.
5. method according to claim 1 is characterized in that, after the braking magnetizing inrush current of described magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient, also comprises: this phase of locking differential protection.
6. method according to claim 1 is characterized in that, the weight of described amplitude bias current is: the ratio of amplitude bias current and fundamental current.
7. method according to claim 1 is characterized in that, the weight of described second harmonic current is respectively: the ratio of second harmonic current and fundamental current.
8. the system of braking magnetizing inrush current in the differential protection of ultra-high voltage transformer is characterized in that, comprising: computing unit, judging unit, transmitting element and brake unit;
Described computing unit is used for calculating every corresponding magnetizing inrush current criterion by the weight of the amplitude bias current of every phase, the weight and the waveform symmetry degree of second harmonic current;
Judging unit is used to judge that whether the described magnetizing inrush current criterion of described computing unit calculating is greater than the braking magnetizing inrush current coefficient;
Described transmitting element is used for sending brake signal to described brake unit when the described magnetizing inrush current criterion of described judgment unit judges during greater than the braking magnetizing inrush current coefficient;
Described brake unit is used to brake the magnetizing inrush current of magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient.
9. system according to claim 8 is characterized in that, described computing unit is used for calculating every corresponding magnetizing inrush current criterion by the weight of the amplitude bias current of every phase, the weight and the waveform symmetry degree of second harmonic current; Concrete by following formula realization:
F (k
0, k
2, D)=C
1k
0+ C
2k
2+ C
3D; k
0Be the weight of described amplitude bias current, k
2Be the weight of described second harmonic current, D is described waveform symmetry degree; C
1, C
2, C
3Be characteristic coefficient.
10. system according to claim 8 is characterized in that, also comprises locking unit, after described brake unit is with the braking magnetizing inrush current of magnetizing inrush current criterion greater than the phase of braking magnetizing inrush current coefficient, is used for the differential protection of this phase of locking.
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|---|---|---|---|
| CN200910168260A CN101764391B (en) | 2009-08-20 | 2009-08-20 | Method and system for braking magnetizing inrush current in differential protection of ultra-high voltage transformer |
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|---|---|---|---|
| CN200910168260A CN101764391B (en) | 2009-08-20 | 2009-08-20 | Method and system for braking magnetizing inrush current in differential protection of ultra-high voltage transformer |
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Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102035178A (en) * | 2010-12-29 | 2011-04-27 | 许继集团有限公司 | Method for transformer excitation surge current latching |
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