CN110048386A - A kind of protection algorism of distribution network failure demand limiter - Google Patents
A kind of protection algorism of distribution network failure demand limiter Download PDFInfo
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- CN110048386A CN110048386A CN201910348939.XA CN201910348939A CN110048386A CN 110048386 A CN110048386 A CN 110048386A CN 201910348939 A CN201910348939 A CN 201910348939A CN 110048386 A CN110048386 A CN 110048386A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/16528—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values using digital techniques or performing arithmetic operations
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
Abstract
A kind of protection algorism of distribution network failure demand limiter, belongs to technical field of power systems, and in particular to a kind of protection algorism of distribution network failure demand limiter.The present invention influences big, the calculating defect that the time is long, computational accuracy is low for existing algorithm attenuating dc component, provides a kind of protection algorism that can effectively filter out attenuating dc component, calculate the distribution network failure demand limiter that the time is short, computational accuracy is high.In the present invention, a distribution network transmission line model is established, according to distribution network transmission line model, establishes MATLAB simulation model；The current signal in distribution network transmission line is acquired in real time: corresponding protection algorism being chosen by collected current signal type, sampled data is handled, measured value is calculated；Measured value and setting valve are compared, starting current limiter limiting short-circuit current.Present invention is mainly used for control demand limiters.
Description
Technical field
The invention belongs to technical field of power systems, and in particular to a kind of protection calculation of distribution network failure demand limiter
Method.
Background technique
With the continuous expansion of electric system scale, power grid is gradually reinforced, and electric system short circuit currents level is climbed year by year
It rises.Powerful short circuit current is to route, equipment and switchs the requirement of dynamic thermal stability itself and gets higher, and power system capacity constantly increases
Greatly, capacity of short circuit and short circuit current also constantly rise, the unlimited starting ability for improving fuse or breaker and unlimited
Raising route, equipment dynamic thermal stability be it is very uneconomical, even not possible with and the limit disjunction number of fuse
It is extremely limited.To limit short circuit current level, fault current limiter enters the technological applications stage as new technical measures.Therefore
Barrier demand limiter does not change trend distribution when operating normally, increase line impedance limiting short-circuit current when detecting failure, point
Influence situation of the fault current limiter to route protection is analysed, the technological means and actual motion that elaboration protective device is taken are adopted
The adjusting measure taken.Being affected of attenuating dc component present in existing algorithm, computational accuracy is low, it is longer to calculate the time
Problem.Existing protection algorism cannot guarantee above-mentioned 3 points requirement simultaneously.
It is therefore desirable to which a kind of can effectively filter out attenuating dc component, calculate the power distribution network that the time is short, computational accuracy is high
The protection algorism of fault current limiter.
Summary of the invention
The present invention influences big, the calculating defect that the time is long, computational accuracy is low for existing algorithm attenuating dc component, provides
It is a kind of effectively to filter out attenuating dc component, calculate the distribution network failure demand limiter that the time is short, computational accuracy is high
Protection algorism.
A kind of technical solution of the protection algorism of distribution network failure demand limiter according to the present invention is as follows:
A kind of protection algorism of distribution network failure demand limiter according to the present invention, it the following steps are included:
Step 1: establishing a distribution network transmission line model, according to distribution network transmission line model, MATLAB emulation mould is established
Type；Current signal in acquisition distribution network transmission line in real time；
Step 2: choosing corresponding protection algorism by collected current signal type, sampled data is handled, is calculated
Measured value out；
Step 3: by measured value ImIt is compared with setting valve I, if ImWhen > > I, when short trouble as occurs, starting electricity
Flow limiter limiting short-circuit current.
Further: in step 1, A, B, C phase current instantaneous value being drawn according to collected current signal in real time Waveform diagram.
Further: in step 2, according to current instantaneous valueAny two-phase of waveform intersection point and mistake
The number of zero point chooses corresponding protection algorism: if intersection point is overlapped with zero crossing, i.e., there are six waypoints for each cycle, use
Six sectionalised protection algorithms handle sampled data, calculate measured value；If intersection point is not overlapped with zero crossing, i.e., each cycle
There are 12 waypoints, sampled data is handled using ten two-section protection algorisms, calculates measured value.
Further: the detailed process of the six sectionalised protections algorithm are as follows:
Each cycle is divided into six sections by six waypoints, and operation time is six/a cycle, chooses the sampling frequency of 120kHz
Rate collection point, since the short-circuit moment, point amplitude of variation corresponding to fundamental current amplitude is identical with fundamental current actual value,
And then remove the influence of attenuating dc component；
According to three-phase shortcircuit formula:
In formula:Respectively A, B, C phase current instantaneous value；Im is fundamental current amplitude, wherein ImA、ImB、ImCPoint
Not Wei A, B, C phase fundamental current amplitude；ω is fundamental wave frequency, and t is the time, and α is starting phase angle；τ is that die-away time is normal
Number；
In the intersection point of the period 1 first any two-phase, when as A phase current is equal with C phase current, it may be assumed that
It arranges:
cos(ωt+α-30°)-cos(α-30°)e-t/τ=0 (3)
T/ τ is considered as 0 within the 0-T/6 period, then e-t/τIt is 1, arrangement obtains:
Wherein f is 50Hz, and starting phase angle α is only related with time t, and time t point is six sectionsTake t=
When 3.33ms, solving starting phase angle α is 0 degree, and starting phase angle α, t are brought into formula and calculates formula (1) respectively and acquires three
Fundamental current amplitude in formula, and averaged, it may be assumed that
Fundamental current amplitude average value are as follows:
By obtained fundamental current amplitude average value ImCompared with setting valve I.
Further: the detailed process of the ten two-sections protection algorism are as follows:
Each cycle is divided into 12 sections by 12 waypoints, and execution cycle was ten half periods
According to three-phase shortcircuit formula:
In formula:Respectively A, B, C phase current instantaneous value；Im is fundamental current amplitude, wherein ImA、ImB、ImCPoint
Not Wei A, B, C phase fundamental current amplitude；ω is fundamental wave frequency, and t is the time, and α is starting phase angle；τ is that die-away time is normal
Number；
In the intersection point of the period 1 first any two-phase, when as A phase current is equal with C phase current, it may be assumed that
It arranges:
cos(ωt+α-30°)-cos(α-30°)e-t/τ=0 (3)
T/ τ is considered as 0 within the time period, then e-t/τIt is 1, arrangement obtains:
Wherein f is 50Hz, and starting phase angle is only related with time t；Time t point is 12 sections,Take t=
When 1.67ms, solving starting phase angle α is 15 degree, and starting phase angle α, t are brought into formula to the base calculated in three formula respectively
Wave current amplitude, and averaged, i.e.,
Fundamental current amplitude average value are as follows:
By obtained fundamental current amplitude average value ImCompared with setting valve I.
A kind of beneficial effect of the protection algorism of distribution network failure demand limiter according to the present invention is:
A kind of protection algorism of distribution network failure demand limiter according to the present invention, can be improved the accurate of evaluation
Degree, protection algorism is improved on the basis of Fourier algorithm, is a kind of novel using transient current fast tripping protection as carrier
Integral algorithm；Sample frequency selects 120kHz, and for the control errors of calculated result within 2%, precision is higher to meet reliability
It is required that；It can reduce and calculate the time；The DC component that decaying can be filtered out extracts fundamental current amplitude, i.e., calculating the time and
Precision, and then eliminate the influence of attenuating dc component；Accuracy is high, and error is can be controlled within 2%.
Detailed description of the invention
Fig. 1 is the flow chart of the protection algorism of distribution network failure demand limiter；
Fig. 2 is six sectionalised protection algorithm flow charts；
Fig. 3 is ten two-section protection algorism flow charts；
Fig. 4 is current waveform figure under normal circumstances,
Current waveform figure when Fig. 5 is three-phase shortcircuit；
Fig. 6 is the three-phase shortcircuit equivalent circuit diagram of power distribution network under normal circumstances；
Fig. 7 is the schematic diagram of progress discrete sampling after integral；
Fig. 8 is six segmented current waveform diagrams；
Fig. 9 is distribution network line illustraton of model；
Figure 10 is distribution network transmission line model M ATLAB simulation model figure；
Figure 11 is the normal current waveform diagram of six sectionalised protection algorithms；
Figure 12 is the three short circuit current waveform diagram of six sectionalised protection algorithms；
Figure 13 is the line to line fault current waveform figure of six sectionalised protection algorithms.
Specific embodiment
Below with reference to embodiment, the following further describes the technical solution of the present invention, and however, it is not limited to this, all right
Technical solution of the present invention is modified or replaced equivalently, and without departing from the spirit and scope of the technical solution of the present invention, should all be contained
Lid is within the protection scope of the present invention.
Embodiment 1
Illustrate the present embodiment in conjunction with Fig. 1-Fig. 3, in the present embodiment, a kind of distribution network failure electric current limit involved in the present embodiment
The protection algorism of device processed, it the following steps are included:
Step 1: establishing a distribution network transmission line model, according to distribution network transmission line model, MATLAB emulation mould is established
Type；Current signal in acquisition distribution network transmission line in real time；
Step 2: choosing corresponding protection algorism by collected current signal type, sampled data is handled, is calculated
Measured value out；
Step 3: by measured value ImIt is compared with setting valve I, if ImWhen > > I, when short trouble as occurs, starting electricity
Flow limiter limiting short-circuit current.
Signal pickup assembly acquires current signal from route in real time, and by using corresponding algorithm, to sampled data
Processing appropriate is carried out, and measured value and setting valve are compared, when short trouble occurs, controller can issue in time
Signal is by switch motion, to reach the target of limiting short-circuit current.In actual short-circuit conditions no matter three-phase shortcircuit or
Line to line fault all includes DC component and AC compounent, therefore should consider that the assessment of protection algorism, decaying can be filtered out
DC component, accurately extract fundamental current amplitude, i.e. calculating time and precision, while being also required to consider the big of operand
The small feasibility to ensure the algorithm.
More specifically: in step 1, A, B, C phase current instantaneous value being drawn according to collected current signal in real timeWaveform diagram.
More specifically: in step 2, according to current instantaneous valueAny two-phase of waveform intersection point and
The number of zero crossing chooses corresponding protection algorism: if intersection point is overlapped with zero crossing, i.e., there are six waypoints for each cycle, adopt
Sampled data is handled with six sectionalised protection algorithms, calculates measured value；If intersection point is not overlapped with zero crossing, i.e., each week
Wave has 12 waypoints, is handled using ten two-section protection algorisms sampled data, calculates measured value.
Cycle is divided into six sections or 12 sections based on Fourier algorithm, calculate the time it is very short meet instant protection requirement,
It can effectively remove simultaneously and the attenuating dc component that short circuit occurs occurs, sample frequency selects 120kHz, the error of calculated result
Within 2%, precision is higher to meet reliability requirement for control.
The detailed process of the six sectionalised protections algorithm are as follows:
Each cycle is divided into six sections by six waypoints, and operation time is six/a cycle, chooses the sampling frequency of 120kHz
Rate collection point, since the short-circuit moment, point amplitude of variation corresponding to fundamental current amplitude is identical with fundamental current actual value,
And then remove the influence of attenuating dc component.
By taking three-phase shortcircuit as an example, Fig. 4 is current waveform figure under normal circumstances, current waveform figure when Fig. 5 is three-phase shortcircuit,
The intersection point of any two-phase, is divided into six sections for each cycle, calculates each segmentation in figure；Or with the intersection point of any two-phase
Each cycle is divided into 12 sections with zero crossing, each segmentation is calculated.The time of both algorithms is respectively 3.33ms
And 1.67ms, it is short to calculate the time.
By simulation result as it can be seen that this new algorithm is since the short-circuit moment, point corresponding to fundamental current amplitude
Amplitude of variation is smaller, basic identical with fundamental current actual value, can remove the influence of attenuating dc component.
Selecting sample frequency is that 120kHz guarantees the control errors of the protection algorism below 2%.
The protection algorism of distribution network failure demand limiter is improved on the basis of Fourier algorithm, with instantaneous electricity
Stream fast tripping protection is carrier, is a kind of novel integral algorithm.
As shown in figure 4, the current waveform figure of three-phase shortcircuit under normal circumstances, with current waveform and three-phase under normal circumstances
The intersection point of any two-phase in short-circuit waveform diagram, is divided into six sections for each cycle, and operation time is about 3.33ms, is 1/6th
Period, or with the intersection point and zero crossing of two-phase any in attached drawing 5, each cycle is divided into 12 sections, operation time is about
1.67ms was ten half periods；To guarantee the accurate of calculated result, the sample frequency collection point of 120kHz is chosen.It is logical
Simulation result is crossed as it can be seen that this new algorithm is since the short-circuit moment, point amplitude of variation corresponding to fundamental current amplitude compared with
It is small, it is basic identical with fundamental current actual value, the influence of attenuating dc component can be removed.
According to three-phase shortcircuit formula:
In formula:Respectively A, B, C phase current instantaneous value；ImFor fundamental current amplitude, wherein ImA、ImB、ImCPoint
Not Wei A, B, C phase fundamental current amplitude；ω is fundamental wave frequency, and t is the time, and α is starting phase angle；τ is that die-away time is normal
Number；
In the intersection point of the period 1 first any two-phase, when as A phase current is equal with C phase current, it may be assumed that
It arranges:
cos(ωt+α-30°)-cos(α-30°)e-t/τ=0 (3)
T/ τ is considered as 0 within the time period, then e-t/τIt is 1, arrangement obtains:
Wherein f is 50Hz, and starting phase angle is only related with time t；Time t point is 12 sections,Take t=
When 1.67ms, solving starting phase angle α is 15 degree, and starting phase angle α, t are brought into formula to the base calculated in three formula respectively
Wave current amplitude, and averaged, i.e.,
Fundamental current amplitude average value are as follows:
By obtained fundamental current amplitude average value ImCompared with setting valve I.
More specifically: the detailed process of the ten two-sections protection algorism are as follows:
Each cycle is divided into 12 sections by 12 waypoints, and execution cycle was ten half periods
According to three-phase shortcircuit formula:
In formula:Respectively A, B, C phase current instantaneous value；Im is fundamental current amplitude, wherein ImA、ImB、ImCPoint
Not Wei A, B, C phase fundamental current amplitude；ω is fundamental wave frequency, and t is the time, and α is starting phase angle；τ is that die-away time is normal
Number；
In the intersection point of the period 1 first any two-phase, when as A phase current is equal with C phase current, it may be assumed that
It arranges:
cos(ωt+α-30°)-cos(α-30°)e-t/τ=0 (3)
T/ τ is considered as 0 within the time period, then e-t/τIt is 1, arrangement obtains:
Wherein f is 50Hz, and starting phase angle is only related with time t；Time t point is 12 sections,Take t=
When 1.67ms, solving starting phase angle α is 15 degree, and starting phase angle α, t are brought into formula to the base calculated in three formula respectively
Wave current amplitude, and averaged, i.e.,
Fundamental current amplitude average value are as follows:
By obtained fundamental current amplitude average value ImCompared with setting valve I.
The short trouble of 10kV power distribution network includes that three-phase shortcircuit, line to line fault, two-phase grounding fault are several under normal circumstances
Situation.
As shown in fig. 6, the equivalent circuit diagram of three-phase shortcircuit, by taking three-phase shortcircuit as an example, we are according to three under normal circumstances
Mutually short-circuit figure obtains three-phase shortcircuit formula；It can derive that three-phase shortcircuit is as shown in formula 1 by three-phase shortcircuit equivalent circuit diagram:
In formula: ImFor fundamental current amplitude, A；α is starting phase angle, degree；τ is damping time constant；ω is fundamental wave frequency,
rad/s；Respectively A, B, C phase current instantaneous value, A.
The intersection point of first any two-phase is the intersection point of A, C two-phase in Fig. 5, and A, C biphase current instantaneous value are equal at this time,
I.e.
It arranges
cos(ωt+α-30°)-cos(α-30°)e-t/τ=0 (3)
Be defaulted as at this time calculate the time it is very short, will be regarded as 0 within the time period, be then 1, arrangement obtains:
F is 50Hz, and starting phase angle is only related with time t；It is divided into six sections of t=3.33ms；It is divided into 12 sections, t=1.67ms takes
When t=1.67ms, solving starting phase angle α is 15 degree.Starting phase angle α, t are brought into formula and calculate three formula (1) respectively
In fundamental current amplitude, and averaged, i.e.,
Fundamental current amplitude average value are as follows:
To obtain more points, when sample frequency takes 12kHz, every cycle acquires 240 points, t=1.67ms, every block sampling point
Number is 20, improves the accuracy of calculating.Due to all cosine amounts of three short circuit current intermediate cam function, for simplicity
Continuous signal multiplied by integrating after a trigonometric function, is become discrete signal using trapezoidal accumulation algorithm by transient current by operation,
Finally add up.It is as follows that simple analysis is carried out with regard to actual principle:
Wherein: i is current instantaneous value to be detected, A；T is that integrating range section calculates time, ms；ImFor fundamental current to be detected
Amplitude, A；α is starting phase angle, degree.
Integral carries out discrete sampling after completing, and trapezoidal summation is recycled to be overlapped:
Wherein: TsFor sampling period, ms；Z is the sampling number in computation interval section；N is the number of sampling points in a cycle；
F is frequency, Hz.
As shown in fig. 7, discrete sampling schematic diagram, by taking A phase as an example, under actual short-circuit conditions, since the short-circuit moment
To A, C two-phase intersection point as first integrating range section, A phase current is integrated and is carried out multiplied by cos (π/12 ω t+)
Discrete sampling process is as follows:
That is:
Similarly, B, C biphase current are respectively multiplied by cos (π/12 ω t-7), cos (π/4 ω t-5), and then integral, discretization obtain:
Obtain fundamental current amplitude are as follows:
It is obtained from formula and a cycle is divided into 12 sections of calculated fundamental current amplitude exact values of first segment.Remaining
Segmentation similarly calculates.
As shown in figure 8, six segmented current waveform diagrams, are illustrated, by a week with the A phase of six discrete methods under normal circumstances
Phase section (- π/6~11 π/6) is divided into six sections, i.e. seven points of a~g are divided into six sections.Calculate the fundamental current amplitude I of A phaseAm, respectively such as
Under:
(1) in the section a~b, corresponding integrating range is-π/6~π/6,
Integral, discrete sampling obtain:
Wherein: TsFor sampling period, unit ms；N is sampling number in a cycle；I (k) is current sample instantaneous value, A.
Simultaneous Equations obtain:
(2) in the section b~c, corresponding integrating range is π/6~pi/2, conclusion are as follows:
(3) in the section c~d, corresponding integrating range is pi/2~5 π/6, conclusion are as follows:
(4) in the section d~e, corresponding integrating range is 5 π/6~7 π/6, conclusion are as follows:
(5) in the section e~f, corresponding integrating range is 7 π/6~3 pi/2s, conclusion are as follows:
(6) in the section f~g, corresponding integrating range is 3 pi/2s~11 π/6, conclusion are as follows:
B, the calculating of C two-phase and A phase be similarly.It is averaged after calculating the fundamental current amplitude of B, C two-phase in practical calculating process
Fundamental current amplitude can be accurately obtained.Calculating the time at this time is six/a cycle, and about 3.33ms, the time is very short, full
The requirement of sufficient quick-action.
Each cycle is divided into 12 sections, and the intersection point and zero crossing of any two-phase of three-phase current have a~n ten in this segment
Three, segment is 0~2 π.Computation interval section be any two-phase intersection point arrive adjacent zero crossing, calculation method with six sections protect
It is identical to protect algorithm.
As shown in figure 9, establishing a distribution network line model according to actual power distribution network, LM sections are open circuit fault section, MN
For non-faulting section.
As shown in Figure 10, in order to more intuitively find out various protection algorisms the characteristics of, foundation distribution network transmission line model,
MATLAB simulation model is established, since the present embodiment is mainly using new algorithm come calculating current, so need to only simulate normal
In the case of and short-circuit conditions under current waveform figure.
Figure 11 is the normal current waveform diagram of six sectionalised protection algorithms；Figure 12 is the three-phase shortcircuit electricity of six sectionalised protection algorithms
Flow waveform diagram；Figure 13 is the line to line fault current waveform figure of six sectionalised protection algorithms；Line to line fault packet in actual short-circuit process
Containing three kinds of situation A, B phase short circuits, the short circuit of B, C phase, A, C phase short circuit, the identical short circuit current for this time only listing A, B phase of three kinds of situations
Waveform diagram.It can obtain from Figure 11-Figure 13 to draw a conclusion, the calculated fundamental current amplitude of the algorithm is constituted under normal circumstances
Be not a continuous straight line, but discrete point because having used discretization process in actual calculating process, these
The position of point is all in the position of A, B, C three-phase crosspoint two-by-two.Since the short-circuit moment, corresponding to fundamental current amplitude
Point amplitude of variation is smaller, basic identical with fundamental current actual value, can remove the influence of DC component；Through analytical calculation,
Control errors are 2% or so.Comprehensively consider, which calculates the time as 3.33ms, meets quick action type protection and requires；Precision compared with
Height meets reliability requirement.Therefore the algorithm compares the performance that existing algorithm has comparative superiority.
Claims (5)
1. a kind of protection algorism of distribution network failure demand limiter, which is characterized in that it the following steps are included:
Step 1: establishing a distribution network transmission line model, according to distribution network transmission line model, MATLAB emulation mould is established
Type；Current signal in acquisition distribution network transmission line in real time；
Step 2: choosing corresponding protection algorism by collected current signal type, sampled data is handled, is calculated
Measured value out；
Step 3: by measured value ImIt is compared with setting valve I, if ImWhen > > I, when short trouble as occurs, starting current
Limiter limiting short-circuit current.
2. a kind of protection algorism of distribution network failure demand limiter according to claim 1, which is characterized in that in step
In one, A, B, C phase current instantaneous value are drawn according to collected current signal in real timeWaveform diagram.
3. a kind of protection algorism of distribution network failure demand limiter according to claim 2, which is characterized in that in step
In two, according to current instantaneous valueThe intersection point of any two-phase of waveform and the number of zero crossing choose corresponding protection
Algorithm: if intersection point is overlapped with zero crossing, i.e., there are six waypoints for each cycle, using six sectionalised protection algorithms to sampled data
It is handled, calculates measured value；If intersection point is not overlapped with zero crossing, i.e., each cycle has 12 waypoints, using 12
Sectionalised protection algorithm handles sampled data, calculates measured value.
4. a kind of protection algorism of distribution network failure demand limiter according to claim 3, which is characterized in that described six
The detailed process of sectionalised protection algorithm are as follows:
Each cycle is divided into six sections by six intersection points, and operation time is six/a cycle, chooses the sample frequency of 120kHz
Collection point, since the short-circuit moment, point amplitude of variation corresponding to fundamental current amplitude is identical with fundamental current actual value, into
And remove the influence of attenuating dc component；
According to three-phase shortcircuit formula:
In formula:Respectively A, B, C phase current instantaneous value；Im is fundamental current amplitude, wherein ImA、ImB、ImCPoint
Not Wei A, B, C phase fundamental current amplitude；ω is fundamental wave frequency, and t is the time, and α is starting phase angle；τ is that die-away time is normal
Number；
In the intersection point of the period 1 first any two-phase, when as A phase current is equal with C phase current, it may be assumed that
It arranges:
cos(ωt+α-300)-cos(α-300)e-t/τ=0 (3)
T/ τ is considered as 0 within the 0-T/6 period, then e-t/τIt is 1, arrangement obtains:
Wherein f is 50Hz, and starting phase angle α is only related with time t, and time t point is six sectionsTake t=
When 3.33ms, solving starting phase angle α is 0 degree, and starting phase angle α, t are brought into formula and calculates formula (1) respectively and acquires three
Fundamental current amplitude in formula, and averaged, it may be assumed that
Fundamental current amplitude average value are as follows:
By obtained fundamental current amplitude average value ImCompared with setting valve I.
5. a kind of protection algorism of distribution network failure demand limiter according to claim 3, which is characterized in that described ten
The detailed process of two-section protection algorism are as follows:
Each cycle is divided into 12 sections by 12 waypoints, and execution cycle was ten half periods
According to three-phase shortcircuit formula:
In formula:Respectively A, B, C phase current instantaneous value；Im is fundamental current amplitude, wherein ImA、ImB、ImCPoint
Not Wei A, B, C phase fundamental current amplitude；ω is fundamental wave frequency, and t is the time, and α is starting phase angle；τ is that die-away time is normal
Number；
In the intersection point of the period 1 first any two-phase, when as A phase current is equal with C phase current, it may be assumed that
It arranges:
cos(ωt+α-300)-cos(α-300)e-t/τ=0 (3)
T/ τ is considered as 0 within the time period, then e-t/τIt is 1, arrangement obtains:
Wherein f is 50Hz, and starting phase angle is only related with time t；Time t point is 12 sections,Take t=
When 1.67ms, solving starting phase angle α is 15 degree, and starting phase angle α, t are brought into formula to the base calculated in three formula respectively
Wave current amplitude, and averaged, i.e.,
Fundamental current amplitude average value are as follows:
By obtained fundamental current amplitude average value ImCompared with setting valve I.
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| CN111064403A (en) * | 2019-12-27 | 2020-04-24 | 绍兴市上虞区理工高等研究院 | Circuit control method and device based on excitation system |
| CN111175670A (en) * | 2019-07-30 | 2020-05-19 | 贵州电网有限责任公司 | Ground fault inversion implementation method of distribution automation test system |
| CN112165078A (en) * | 2020-06-15 | 2021-01-01 | 国网湖北省电力有限公司黄冈供电公司 | Resonant current limiter input control method utilizing short-circuit current change rate |
| CN114019231A (en) * | 2021-11-04 | 2022-02-08 | 国网湖南省电力有限公司 | Attenuated direct current extraction method for direct current electric energy metering |
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| CN112165078B (en) * | 2020-06-15 | 2022-07-05 | 国网湖北省电力有限公司黄冈供电公司 | Resonant current limiter input control method utilizing short-circuit current change rate |
| CN114019231A (en) * | 2021-11-04 | 2022-02-08 | 国网湖南省电力有限公司 | Attenuated direct current extraction method for direct current electric energy metering |
| CN114019231B (en) * | 2021-11-04 | 2023-08-18 | 国网湖南省电力有限公司 | Attenuation direct current extraction method for direct current electric energy metering |
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