CN106129966B - The method and device for preventing transformer differential protection malfunction based on coefficient of kurtosis - Google Patents
The method and device for preventing transformer differential protection malfunction based on coefficient of kurtosis Download PDFInfo
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- CN106129966B CN106129966B CN201610562893.8A CN201610562893A CN106129966B CN 106129966 B CN106129966 B CN 106129966B CN 201610562893 A CN201610562893 A CN 201610562893A CN 106129966 B CN106129966 B CN 106129966B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/045—Differential protection of transformers
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Abstract
The invention discloses the method and device for preventing transformer differential protection malfunction based on coefficient of kurtosis, method includes：Obtain the instantaneous sampling value of secondary current；Judge whether to break down；Obtain the waveform of each phase difference current；Form the combined waveform of each phase difference current；The coefficient of kurtosis of combined waveform described in each phase difference current of calculating transformer；Judge that whether there is or not current transformers to be saturated during transformer fault；It is latched transformer differential protection；Open transformer differential protection.The present invention carries out proper transformation by the portion waveshape to difference current; and it is extracted in area using coefficient of kurtosis, the difference current wave character of external area error; coefficient of kurtosis is compared with coefficient of kurtosis definite value; can accurately identify troubles inside the sample space and current transformer seriously be saturated, be generally saturated, it is less saturated in the case of external area error, the malfunction of differential protection when effectivelying prevent transformer external area error caused by CT saturation.
Description
Technical field
The invention belongs to technical field of power systems, more particularly to prevent transformer differential protection from missing based on coefficient of kurtosis
Dynamic method and device.
Background technology
Survey of the class P current transformer (CT) as the lower primary current of electric system abnormal running or malfunction
Equipment is measured, China 220kV and following system are widely used in.P grades of current transformers can ensure that systematic steady state is run in type selecting
When the progress of disease accuracy, and make its progress of disease error be no more than specified value, but cannot be guaranteed the transient process progress of disease accuracy.System
When failure of uniting, primary current may be the dozens to one hundred times of normal operating current, and include the direct current by exponential damping law
Therefore component, the operating point of current transformer core can occur to change on a large scale between linear zone and inelastic region, make electricity
Current transformer is saturated, and cannot accurately measure progress of disease system primary current, can not really reflect the actual current of primary system,
For the protective relaying device of acquisition Current Transformer Secondary side electric current, easily there is malfunction, tripping or deferred action, sternly
The safe and stable operation of power grid is endangered again.
Transformer is the core equipment of AC transmission system, and main protection of the differential protection as transformer troubles inside the sample space is answered
Ensure the reliability of its action.But in running at the scene, differential protection malfunction event happens occasionally, each side Current Mutual Inductance of transformer
It is the one of the major reasons for causing external area error time difference stream to significantly increase and then differential protection being made malfunction occur that saturation, which occurs, in device, must
Certain measure must be taken to identify CT saturation and carry out the reliability that protection blocking just can guarantee differential protection.
Currently, being had proposed excessively for the maloperation situation for preventing CT saturation from transformer differential protection being caused to occur
Kind technology, such as (Pu south hardwood, Zhai Xuefeng, Yuan Yubo wait .P grades of TA saturations to the differential guarantor of digital ratio-restrained characteristic to Pu south hardwood
Influence [J] Electric Power Automation Equipments of shield, 2003,23 (04):It 76-80.) proposes to start with from differential protection acting characteristic, to this
There is body the ratio-restrained characteristic of certain anti-saturation ability to be modified, and raise restraint coefficient.But the raising of restraint coefficient will be same
When reduce the sensitivity of transformer troubles inside the sample space, therefore many domestic and foreign scholars are based on the secondary electricity before and after CT saturation
The interruption angular difference of stream different wave shape, harmonic content difference or difference current proposes that the saturation detection of a variety of current transformers is calculated
Method.(Shen Quanrong, Yan Wei, Liang Qianbing wait asynchronous method CT saturations to differentiate new principle and its application to such as Shen Quanrong
[J] Automation of Electric Systems, 2005,29 (16):The moment 84-86.) is occurred by precise positioning failure and difference current is apparent
At the time of increase, and judge whether the two synchronizes, whether detection current transformer is saturated, but when current transformer occurs sternly
When being saturated again, current transformer enter saturation time will be less than 1/4 cycle, failure occur the moment be differed very with difference current
It is small.On the other hand, current transformer testing result may be caused to malfunction due to timi requirement inaccuracy, and then lead to differential protection
Malfunction.(Li Guicun, Liu Wanshun, Jia Qingquan wait using the new method of Principle of Wavelet detection CT saturation to Li Guicun etc.
[J] Automation of Electric Systems, 2001,26 (05):36-39+44.) by wavelet transformation saturation detection method, according to Current Mutual Inductance
Whether the otherness detection current transformer of device secondary current Wavelet Modulus Maxima is saturated, but in current zero-crossing point and window
Critical part, Wavelet Detection method are likely to occur relatively large deviation, influence final saturation detection result.(Wang Zhihong, the Zheng Yu such as Wang Zhihong
It is flat, congratulate saturation [J] Power System and its Automation that family Lee determines current transformer in bus protection by calculating harmonic ratio
Journal, 2000,12 (5):19-24.) detect whether current transformer goes out by the harmonic ratio of calculating current mutual inductor secondary current
It is now saturated, but increases calculation amount to varying degrees, reduce the reliability of saturation detection.E.M.dos Santos etc.
(E.M.dos Santos,G.Cardoso Jr.,P.E.Farias and et al.CT saturation detection
based on the distance between consecutive points in the plans formed by the
secondary current samples and their difference-functions[J].IEEE Transactions
on Power Delivery,2013,28(1):29-37.) pass through the multistage difference of calculating current mutual inductor secondary current sampled value
Score value detection current transformer enters saturation point and to move back saturation point, but poor anti jamming capability, reduces saturation detection and differential guarantor
The reliability of shield action.
Therefore, it is necessary to find more rapidly, it is more acurrate, using less parameter method detection CT be saturated to prevent transformer
There is malfunction in differential protection when external area error, and achievement in research can be used as the beneficial benefit of existing CT saturation detection scheme
It fills, helps to improve the rapidity and reliability of differential protection.
Invention content
In view of the above-mentioned problems, the present invention proposes a kind of side for preventing transformer differential protection malfunction based on coefficient of kurtosis
Method and device, solving existing prevents the sensitivity of transformer differential protection malfunction method is low, operand is big, reliability is low to lack
It falls into.
To achieve the goals above, technical solution of the present invention is as follows：
A method of transformer differential protection malfunction is prevented based on coefficient of kurtosis, including：
Step S1：Obtain transformer star lateral areas, angle lateral areas each phase current mutual inductor secondary current instantaneous sampling value.
Step S2：Judge whether transformer breaks down according to the instantaneous sampling value of the secondary current；If it has, then holding
Row step S3；If it has not, thening follow the steps S7.
Step S3：According to each phase difference current instantaneous value of the instantaneous sampling value calculating transformer of the secondary current, and
The waveform of each phase difference current is instantaneously worth to according to difference current described in each phase.
Step S4：Form the combined waveform of each phase difference current of transformer.
Step S5：The coefficient of kurtosis of combined waveform described in each phase difference current of calculating transformer.
Step S6：Judge that whether there is or not current transformers to be saturated during transformer fault：Judge any phase of transformer
The coefficient of kurtosis whether be more than coefficient of kurtosis definite value；If it has, then having current transformer during judgement transformer fault
It is saturated, and executes step S7；If it has not, there is no current transformer to be saturated during then judging transformer fault, and
Execute step S8.
Step S7：It is latched transformer differential protection.
Step S8：Open transformer differential protection.
Further, while executing step S3, the moment occurs for record failure.
Further, step S4 includes：
Step S401：First extreme point is recorded after difference current described in each phase significantly increases at the time of correspond to.
Step S402：It intercepts difference current described in each phase and states first extreme point pair to described from the failure generation moment
Answer the waveform between the moment.
Step S403：The moment occurs as origin using the failure, the difference current waveform that each phase is intercepted is about origin pair
Claim, obtains the difference current waveform after rotation transformation.
Step S404：By the difference current waveform combination of difference current waveform and former interception after each phase rotation transformation.
Step S405：By it is each it is combined after difference current waveform be normalized respectively by amplitude, formed each phase with therefore
The combined waveform centered on moment occurs for barrier.
Further, in step s 2, described to judge whether transformer breaks down, including：Judge described in any one phase
Whether the real-time change amount of secondary current is more than preset starting current；If it has, then judgement transformer breaks down；If
It is no, then judges that transformer does not break down.
Further, coefficient of kurtosis is the fourth central of combined waveform away from the ratio between the bipyramid with standard deviation.
Further, 0.2 times of starting current equal to transformer rated current.
Further, step S402：Using data window intercept difference current described in each phase from the failure occur the moment to
It is described to state first extreme point and correspond to waveform between the moment.
A kind of device for preventing transformer differential protection malfunction based on coefficient of kurtosis, including secondary current acquisition module,
Transformer fault detection module, difference current generation module, difference current composite module, coefficient of kurtosis computing module, mutual inductor
Saturation detection module, differential protection drive mould.
The secondary current of each phase current mutual inductor of the secondary current acquisition module for obtaining transformer star lateral areas, angle lateral areas
Instantaneous sampling value.Transformer fault detection module is for judging whether transformer breaks down；If it has, then controlling differential electricity
Flow generation module；If it has not, then controlling differential protection drive module sends out differential protection block signal.Difference current generation module
For the instantaneous value according to each phase difference current of the instantaneous sampling value calculating transformer of the secondary current, and according to each difference
The waveform for being instantaneously worth to each phase difference current of streaming current.Difference current composite module is used to form the group of each phase difference current
Multiplex shape.The coefficient of kurtosis of combined waveform described in each phase difference current of the coefficient of kurtosis computing module for calculating transformer.Mutually
Sensor saturation detection module is for judging that whether there is or not current transformers to be saturated during transformer fault：Judge that transformation is had a high regard for
Whether the coefficient of kurtosis of one phase is more than coefficient of kurtosis definite value；If it has, then having electric current mutual during judgement transformer fault
Sensor is saturated, and is controlled differential protection drive module and sent out differential protection block signal；If it has not, then judging transformer event
There is no current transformer to be saturated during barrier, and controls differential protection drive module and send out differential protection clearing signal.Difference
Dynamic protection drive module is for controlling being turned on and off for transformer differential protection circuit.
Further, difference current composite module includes sequentially connected extreme point recording unit, interception unit, rotation change
Change unit, assembled unit, normalization unit.
Extreme point recording unit for record difference current described in each phase significantly increase after first extreme point it is corresponding when
It carves.Interception unit states first extreme point correspondence for intercepting difference current described in each phase from the failure generation moment to described
Waveform between moment.Rotation transformation unit is used to that the moment to occur as origin using the failure, the difference current that each phase is intercepted
Waveform obtains the difference current waveform after rotation transformation about origin symmetry.Assembled unit is used for will be after each phase rotation transformation
The difference current waveform combination of difference current waveform and former interception.Normalization unit be used for by it is each it is combined after difference current wave
Shape is normalized by amplitude respectively, forms the combined waveform of each phase centered on the failure generation moment.
Further, coefficient of kurtosis is the fourth central of combined waveform away from the ratio between the bipyramid with standard deviation.
The beneficial effects of the present invention are：
The present invention carries out proper transformation by the portion waveshape to difference current, and is extracted in area using coefficient of kurtosis, area
Coefficient of kurtosis is compared with coefficient of kurtosis definite value, can accurately identify troubles inside the sample space by the difference current wave character of outer failure
Seriously be saturated with current transformer, general saturation, it is less saturated in the case of external area error, effectively prevent CT saturation
The malfunction of differential protection when caused transformer external area error；And algorithm is simple, quick, reliability is high, it is ensured that relay protection
Reliability, the rapidity of device, can be used as the useful supplement of existing saturation detection algorithm, have certain practical meaning in engineering.
Description of the drawings
Fig. 1 is the flow diagram of the method for preventing transformer differential protection malfunction based on coefficient of kurtosis.
Fig. 2 is the difference stream combined waveform figure after rotation transformation, combination.
Fig. 3 is the analogous diagram of electric system in embodiment.
Fig. 4 is transformer star side A, B phase current waveform in embodiment.
Fig. 5 is transformer angle side A phase current waveforms in embodiment.
It is transformer A difference stream waveforms that Fig. 6, which is in embodiment,.
Fig. 7 is the block diagram of the equipment for preventing transformer differential protection malfunction based on coefficient of kurtosis.
Specific implementation mode
Below in conjunction with the accompanying drawings, it elaborates to embodiment.
When transformer troubles inside the sample space, difference current have current moment be and failure occur timing synchronization；Outside transformer area
When failure, if different degrees of saturation occurs in both sides current transformer, difference current will be made to significantly increase, easily differential protection is made to miss
It is dynamic, but it with the failure generation moment is nonsynchronous that difference current, which significantly increases the moment, in such cases, i.e., and there are bright for difference current
Aobvious interval angle.
The present invention according in above-mentioned transformer area, external area error when difference current wave character, propose be based on statistics
The CT saturation recognition methods of middle coefficient of kurtosis and device.
As shown in Figure 1, for the flow diagram of the method for the invention, this method includes：
Step S1：Obtain transformer star lateral areas, angle lateral areas each phase current mutual inductor secondary current instantaneous sampling value.
Step S2：Judge whether transformer breaks down：Judge the real-time change amount Δ I of secondary current described in any one phaseφIt is whether big
In preset starting current IQD；If it has, then judgement transformer breaks down, the moment occurs for record failure, and executes step
Rapid S3；If it has not, then judging that transformer does not break down, and execute step S7.Step S3：According to the instantaneous of the secondary current
The instantaneous value of each phase difference current of sampled value calculating transformer, and it is each mutually differential according to being instantaneously worth to for each phase difference current
The waveform of electric current.Step S4：Form the combined waveform of each phase difference current of transformer.Step S5：Each phase of calculating transformer
The coefficient of kurtosis of combined waveform described in difference current.Step S6：Judge that whether there is or not current transformers to go out during transformer fault
Now it is saturated：Judge whether the coefficient of kurtosis of any phase of transformer is more than coefficient of kurtosis definite value；If it has, then judgement transformer
There is current transformer to be saturated in failure process, and executes step S7；If it has not, not having during then judging transformer fault
Current transformer is saturated, and executes step S8.Step S7：It is latched transformer differential protection.Step S8：Open transformer is poor
Dynamic protection.
It describes in detail below to the present invention by taking the transformer Y0d11 modes of connection as an example.
Specifically, in step S1, the secondary current of transformer star lateral areas, angle lateral areas threephase current transformer is adopted
80 point sampling of cycle, i.e. sample frequency f is arranged in samples=4kHz.
In step S2, judge whether transformer breaks down according to difference of phase currents start-up criterion.So-called phase current is prominent
Variable start-up criterion refers to whether the variable quantity of any phase current of transformer is more than the starting current I of settingQD, if it is greater than then poor
Dynamic protection starts.
Specifically, calculating transformer star lateral areas, any phase in angle lateral areas real-time phase current variation delta Iφ(k), if transformation
Any phase current variation delta I in device star lateral areas, angle lateral areasφ(k) it is more than the starting current I of settingQD, then judge to break down,
And it records failure and the moment occurs as tf=k/fs, differential protection start, enter step (3)；Otherwise return to step S1 continues to sample.
Phase current variation delta I is setφSudden Changing Rate start-up criterion：
ΔIφ>IQD (1)
Wherein phase current variation delta IφWith starting current IQDCalculation formula be：
Wherein φ refers to A, B, C three-phases, iφ(k) it is the instantaneous value of k-th of sampled point φ phase phase current, Ie is that change is arrived in conversion
The rated current of depressor star side, iφ(k), Ie is the current value of Current Transformer Secondary side.
In step S3, according to the transformer star lateral areas of step (1) acquisition, the electricity of angle lateral areas threephase current transformer secondary side
Instantaneous value is flowed, Three-Phase Transformer difference current instantaneous value i is calculateddA, idB, idC：
idA=(iYA-iYB)+idA
idB=(iYB-iYC)+idB
idC=(iYC-iYA)+idC (3)
Wherein, iYA, iYB, iYCFor transformer star side threephase current transformer secondary side current instantaneous sampling value；idA, idB,
idCFor transformer angle side threephase current transformer secondary side current instantaneous sampling value.
In step S4, the portion waveshape of each phase difference current of transformer is intercepted, to the portion of each phase difference current of interception
Partial wave shape carries out rotation transformation, and each phase difference current waveform after transformation is carried out group with the former difference current waveform intercepted
It closes, and is normalized by amplitude, form the combined waveform.
Specifically, step S4 is comprised the steps of：Step S401：It records first after difference current described in each phase significantly increases
At the time of a extreme point corresponds to；Step S402：It intercepts difference current described in each phase and occurs the moment from the failure and state the to described
One extreme point corresponds to the waveform between the moment；Step S403：The moment occurs as origin using the failure, the difference that each phase is intercepted
Streaming current waveform obtains the difference current waveform after rotation transformation about origin symmetry；Step S404：After each phase rotation transformation
Difference current waveform and former interception difference current waveform combination；Step S405：By it is each it is combined after difference current waveform
It is normalized respectively by amplitude, forms the combined waveform of each phase centered on the failure generation moment.
In step S402 before intercepting waveform, first data window of the setting for data intercept, institute is intercepted using data window
The waveform needed.Described in step S405 the data after will combining divided by the maximum amplitude in data window are normalized by amplitude.Number
Belong to the prior art according to window, is not repeated.In step S401, obtaining for rear first extreme point is significantly increased about difference current
It takes, the threshold value of a difference current can be pre-set, after difference current is more than the threshold value, record the pole that electric current is reached
It is worth point, as first extreme point after difference current increase.Fig. 2 is the difference current composite wave after rotation transformation, combination
Shape figure.
In step S5, the fourth central of the coefficient of kurtosis, that is, combined waveform figure away from the ratio between the bipyramid with standard deviation, with
Kur indicates that calculation formula is as follows：
In formula：N indicates total sampling number that difference stream combined waveform includes, xiIndicate the difference current of each sampled point,Table
Show that the average value of combination difference current electric current, i are ith sample point.
It is 1.8 to preset coefficient of kurtosis definite value；Calculate the kurtosis system of each phase difference current combined waveform of transformer
After number, in step s 6, each phase coefficient of kurtosis is compared with coefficient of kurtosis definite value；If the coefficient of kurtosis of any phase of transformer
More than coefficient of kurtosis definite value, then judge there is current transformer to be saturated in failure process；Otherwise, it is determined that not have in failure process
There is current transformer to be saturated.
CT saturation refers to current transformer after electric current is more than a certain range, can lead to core sataration.Iron core
When last coil passes through electric current, exciting current generates magnetic flux in the core, and the variation of magnetic flux generates transformation on secondary coil
Electric current afterwards.Exciting current is excessive, is more than after certain value, and the magnetic resistance in iron core can decline, and iron core can be saturated, and the increase of electric current will
Magnetic flux cannot be obviously increased, the electric current of first and second coil proportional cannot change, and magnetic flux saturation, i.e. electric current have occurred at this time
Mutual inductor is saturated.
When thering is current transformer to be saturated during judging transformer fault, then step S7 is carried out, is latched transformer
Differential protection；Otherwise, step S8, open transformer differential protection are carried out.
Technical scheme of the present invention is introduced by a specific embodiment further below.
Present case considers most serious situation, i.e., high voltage side of transformer current transformer is arranged in case and is not saturated, low
Pressure side B, C phase current mutual inductor is not saturated, and only carries out detailed analysis to A phase current mutual inductors saturation and A phase difference currents,
But the Simplified analysis has no effect on the reliability and correctness when present invention application.
(1) 220kV two-terminal transmission systems are established, as shown in figure 3, transformer is Y0d-11 wiring, capacity is analogous diagram
The current transformer of 240MVA, no-load voltage ratio 220/38.5kV, transformer both sides use the simulation model based on J-A theories, weekly
80 point sampling of wave.
(2) three phase short circuit fault, high-pressure side A, B phase current waveform such as Fig. 4 institutes occur outside the lateral areas of transformer angle for 0.5685s
Show, low-pressure side A phase current waveforms are as shown in figure 5, corresponding A phases difference current is as shown in Figure 6.
(3) portion waveshape of interception difference current carries out rotation transformation, and the difference current waveform after transformation is cut with former
The difference current waveform combination taken, and be normalized by amplitude, the combined waveform centered on the failure generation moment is formed, such as
Shown in Fig. 2.
(4) coefficient of kurtosis for calculating combined waveform in step (3), obtains Kur=6.7534, and coefficient of kurtosis definite value is
1.8。
(5) it since Kur is more than coefficient of kurtosis definite value, can determine whether out that transformer both sides current transformer is saturated, be latched
Differential protection.
Fig. 7 is the block diagram of the described device of the present invention, which includes：Secondary current acquisition module 1, transformer
Fault detection module 2, difference current generation module 3, difference current composite module 4, coefficient of kurtosis computing module 5, mutual inductor are full
With detection module 6, differential protection drive module 7.
Secondary current acquisition module 1, transformer fault detection module 2, difference current generation module 3, difference current combination
Module 4, coefficient of kurtosis computing module 5, mutual inductor saturation detection module 6, differential protection drive module 7 are sequentially connected；And become
Depressor fault detection module 2 is connected with differential protection drive module 7.
The secondary electricity of each phase current mutual inductor of the secondary current acquisition module 1 for obtaining transformer star lateral areas, angle lateral areas
The instantaneous sampling value of stream.
Transformer fault detection module 2 is for judging whether transformer breaks down：Judge secondary electricity described in any one phase
The real-time change amount Δ I of streamφWhether preset starting current I is more thanQD；If it has, then judgement transformer breaks down, remember
It records failure and the moment occurs, and control difference current generation module 3；If it has not, then judging that transformer does not break down, and control difference
Dynamic protection drive module 7 sends out differential protection block signal.
Difference current generation module 3 is used for according to each mutually differential of the instantaneous sampling value calculating transformer of the secondary current
The instantaneous value of electric current, and according to the waveform for being instantaneously worth to each phase difference current of each phase difference current；
Difference current composite module 4 is used to form the combined waveform of each phase difference current.
The coefficient of kurtosis of combined waveform described in each phase difference current of the coefficient of kurtosis computing module 5 for calculating transformer.
Mutual inductor saturation detection module 6 is for judging that whether there is or not current transformers to be saturated during transformer fault：
Judge whether the coefficient of kurtosis of any phase of transformer is more than coefficient of kurtosis definite value；If it has, then judgement transformer fault mistake
There is current transformer to be saturated in journey, and controls differential protection drive module 7 and send out differential protection block signal；If it has not,
Then judge there is no current transformer to be saturated during transformer fault, and control differential protection drive module 7 send out it is differential
Protect clearing signal.
Differential protection drive module 7 is for controlling being turned on and off for transformer differential protection circuit.When differential protection drives
When dynamic model block 7 sends out differential protection block signal, transformer differential protection circuit does not work；.When differential protection drive module 7 is sent out
When going out differential protection clearing signal, transformer differential protection circuit is started to work.
Wherein, difference current composite module 4 includes sequentially connected extreme point recording unit, interception unit, rotation transformation
Unit, assembled unit, normalization unit.
Extreme point recording unit for record difference current described in each phase significantly increase after first extreme point it is corresponding when
It carves.Interception unit states first extreme point correspondence for intercepting difference current described in each phase from the failure generation moment to described
Waveform between moment.Rotation transformation unit is used to that the moment to occur as origin using the failure, the difference current that each phase is intercepted
Waveform obtains the difference current waveform after rotation transformation about origin symmetry.Assembled unit is used for will be after each phase rotation transformation
The difference current waveform combination of difference current waveform and former interception.Normalization unit be used for by it is each it is combined after difference current wave
Shape is normalized by amplitude respectively, forms the combined waveform of each phase centered on the failure generation moment.
This embodiment is merely preferred embodiments of the present invention, but scope of protection of the present invention is not limited thereto,
Any one skilled in the art in the technical scope disclosed by the present invention, the change or replacement that can be readily occurred in,
It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with scope of the claims
Subject to.
Claims (8)
1. a kind of method for preventing transformer differential protection malfunction based on coefficient of kurtosis, which is characterized in that including：
Step S1：Obtain transformer star lateral areas, angle lateral areas each phase current mutual inductor secondary current instantaneous sampling value；
Step S2：Judge whether transformer breaks down according to the instantaneous sampling value of the secondary current；If it has, then executing step
Rapid S3；If it has not, thening follow the steps S7；
Step S3：According to each phase difference current instantaneous value of the instantaneous sampling value calculating transformer of the secondary current, and according to
Difference current described in each phase is instantaneously worth to the waveform of each phase difference current；
Step S4：Form the combined waveform of each phase difference current of transformer；
Step S5：The coefficient of kurtosis of combined waveform described in each phase difference current of calculating transformer；
Step S6：Judge that whether there is or not current transformers to be saturated during transformer fault：Judge the institute of any phase of transformer
State whether coefficient of kurtosis is more than coefficient of kurtosis definite value；If it has, then having current transformer appearance during judgement transformer fault
Saturation, and execute step S7；If it has not, there is no current transformer to be saturated during then judging transformer fault, and execute
Step S8；
Step S7：It is latched transformer differential protection；
Step S8：Open transformer differential protection；
The coefficient of kurtosis is the fourth central of the combined waveform away from the ratio between the bipyramid with standard deviation.
2. the method for preventing transformer differential protection malfunction based on coefficient of kurtosis according to claim 1, it is characterised in that：
While executing step S3, the moment occurs for record failure.
3. the method for preventing transformer differential protection malfunction based on coefficient of kurtosis according to claim 2, it is characterised in that：
The step S4 includes：
Step S401：First extreme point is recorded after difference current described in each phase significantly increases at the time of correspond to；
Step S402：It intercepts difference current described in each phase and corresponds to the moment to first extreme point from the failure generation moment
Between waveform；
Step S403：The moment occurs as origin using the failure, the difference current waveform that each phase is intercepted is obtained about origin symmetry
Difference current waveform after to rotation transformation；
Step S404：By the difference current waveform combination of difference current waveform and former interception after each phase rotation transformation；
Step S405：By it is each it is combined after difference current waveform be normalized respectively by amplitude, form each phase and sent out with failure
The combined waveform centered on the raw moment.
4. the method for preventing transformer differential protection malfunction based on coefficient of kurtosis according to claim 1, it is characterised in that：
It is described to judge whether transformer breaks down in the step S2, including：
Judge the real-time change amount Δ I of secondary current described in any one phaseφWhether preset starting current I is more thanQD；
If it has, then judgement transformer breaks down；If it has not, then judging that transformer does not break down.
5. the method for preventing transformer differential protection malfunction based on coefficient of kurtosis according to claim 4, it is characterised in that：
The starting current IQDEqual to 0.2 times of transformer rated current Ie.
6. the method for preventing transformer differential protection malfunction based on coefficient of kurtosis according to claim 3, it is characterised in that：
The step S402：Difference current described in each phase is intercepted using data window, the moment occurs to described first from the failure
Extreme point corresponds to the waveform between the moment.
7. a kind of device for preventing transformer differential protection malfunction based on coefficient of kurtosis, which is characterized in that including：
Secondary current acquisition module (1), transformer fault detection module (2), difference current generation module (3), difference current group
Mold block (4), coefficient of kurtosis computing module (5), mutual inductor saturation detection module (6), differential protection drive module (7)；
The secondary current of each phase current mutual inductor of the secondary current acquisition module (1) for obtaining transformer star lateral areas, angle lateral areas
Instantaneous sampling value；
Transformer fault detection module (2) is for judging whether transformer breaks down；If it has, then control difference current generates
Module (3)；If it has not, then controlling differential protection drive module (7) sends out differential protection block signal；
Difference current generation module (3) is used for each mutually differential electricity of the instantaneous sampling value calculating transformer according to the secondary current
The instantaneous value of stream, and according to the waveform for being instantaneously worth to each phase difference current of each phase difference current；
Difference current composite module (4) is used to form the combined waveform of each phase difference current；
The coefficient of kurtosis of combined waveform described in each phase difference current of the coefficient of kurtosis computing module (5) for calculating transformer；
Mutual inductor saturation detection module (6) is for judging that whether there is or not current transformers to be saturated during transformer fault：Sentence
Whether the coefficient of kurtosis of any phase of disconnected transformer is more than coefficient of kurtosis definite value；If it has, then judgement transformer fault process
In there is current transformer to be saturated, and control differential protection drive module (7) and send out differential protection block signal；If it has not,
Then judge there is no current transformer to be saturated during transformer fault, and controls differential protection drive module (7) and send out difference
Dynamic protection clearing signal；
Differential protection drive module (7) is for controlling being turned on and off for transformer differential protection circuit；
The coefficient of kurtosis is the fourth central of the combined waveform away from the ratio between the bipyramid with standard deviation.
8. the device for preventing transformer differential protection malfunction based on coefficient of kurtosis according to claim 7, it is characterised in that：
Difference current composite module (4) includes sequentially connected extreme point recording unit, interception unit, rotation transformation unit, group
Close unit, normalization unit；
The extreme point recording unit for record difference current described in each phase significantly increase after first extreme point it is corresponding when
It carves；
For intercepting difference current described in each phase from the failure occurs for the interception unit to first extreme point the moment
Waveform between the corresponding moment；
The rotation transformation unit is used to the moment occur as origin using the failure, difference current waveform that each phase is intercepted about
Origin symmetry obtains the difference current waveform after rotation transformation；
The assembled unit is used for the difference current waveform combination of difference current waveform and former interception after each phase rotation transformation；
The normalization unit be used for by it is each it is combined after difference current waveform be normalized respectively by amplitude, form each phase
The combined waveform centered on the failure generation moment.
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| CN111030051B (en) * | 2019-11-26 | 2021-10-08 | 国网江苏省电力有限公司检修分公司 | Differential protection method |
| CN113315104B (en) * | 2021-07-14 | 2022-05-17 | 保定钰鑫电气科技有限公司 | Method for reducing differential protection misoperation |
| CN114172134B (en) * | 2021-12-14 | 2024-05-24 | 四方继保（武汉）软件有限公司 | Differential protection self-synchronization method and system based on zero crossing point of pre-fault waveform |
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