CN105137220B - A kind of CT saturation detection method based on waveform area accounting method - Google Patents
A kind of CT saturation detection method based on waveform area accounting method Download PDFInfo
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Abstract
A kind of CT saturation detection method based on waveform area accounting method, first samples the secondary side current of current transformer；Secondly a standard sine current waveform is defined, the secondary side current of practical saturation is normalized on the basis of maximum value, calculates to obtain the area that is surrounded of the two and time shaft；The two area ratio is calculated again；Finally output is as a result, multilevel iudge.Emphasis of the present invention solves the problems, such as that detection rates are slow during current transformer generation saturation, accuracy of detection is low; the sampled data in half cycles can be utilized; by the saturation behavior of area accounting Sensitive Detection CT, the stability of relay protection work is improved to a certain extent.
Description
Technical field
The invention belongs to the technical field of relay protection of electric system, more particularly to a kind of electricity based on waveform area accounting
Current transformer saturation detection method.
Background technology
Current transformer (Current Transformer, CT) is measuring apparatus important in electric system, normal to transport
Row is directly related to the safety of electric system.Present 220kV and above are required using duplicate system retrofit, temporary in the past
The relatively poor P grade current transformers of state property energy will also complete protection task.Repeatedly occur due to primary electricity in scene
It flows through and causes CT saturations greatly, secondary current is caused to distort, the final accident for occurring to protect tripping of bypassing the immediate leadership.Therefore, CT saturation problems
One of hot issue of electric system researcher concern is become.
For common electromagnetic type current transformer, purposes is to realize the transformation of tested current value, with common transformer
Unlike, output capacity very little is usually no more than tens of volt-ampere.Regardless of it is Verification of Measuring Current Transformer or protection
Current Transformer requires that it can correct progress of disease primary current.Especially in transformer differential protection, the angle of current transformer
Color is more important.But because current power system capacity is increasing, fault current is larger, and usually contains larger non-week
Phase component.Meanwhile current transformer, towards small, direction simple in structure is developed, and current transformer inevitably occurs
Saturated phenomenon.This can generate electric system important equipment greatly harm, even result in the malfunction of relay protection or refuse
Dynamic, consequence is hardly imaginable.Therefore, it can correctly identify whether current transformer occurs saturation in a short time, be relay protection dress
Put the basis of action message.
At present, in order to overcome the harmful effect caused by CT saturations, the solution proposed so far mainly include with
Lower two：First, from current transformer, using the more superior current transformer of anti-saturation performance.As TP class electric currents are mutual
Sensor fully considers the influence of short circuit current direct-flow offset weight when developing, so as to ensure under the transient condition of most serious not
Saturation occurs.But this kind of mutual inductor size is big, cost is high, it is high that objective condition is required.Second is that design inhibits iron core saturation
Algorithm, realize locking in time, and then using backoff algorithm distortion current is compensated also to be considered and CT saturations is inhibited to be made
Into dysgenic effective way.Domestic and international common CT saturation detection algorithms mainly include the CT saturations inspection based on calculus of finite differences
It surveys, can refer to Zhang Xingang, " corrective measure of difference Cutoff current mutual inductor saturation " (North China that Wang Zezhong, Xu Chunli etc. are delivered
Electric power college journal, 2005,32 (5):1-6)；CT saturation detections based on harmonic ratio, can refer to Wang Zhihong, Zheng Yuping, He Jia
" saturation that current transformer in bus protection is determined by calculating harmonic ratio " (Power System and its Automation that Lee etc. delivers
Report, 2010,12 (5):19-24)；CT saturation detection based on virtual impedance model, can refer to Zhao Yongbin, Lu Yuping
Etc. " the current transformer criterion based on virtual impedance model " (Electric Power Automation Equipment, 2007,27 (9) delivered:43-52)；
CT saturation detections based on wavelet transformation, can refer to Cao Yuning, Li Yongli, Zhang Xinghua, and what Mei Yun etc. was delivered " is based on wavelet transformation
CT saturation detect new criterion in real time " (Automation of Electric Systems, 2001,25 (10):27-30)；Based on mathematics shape
The CT saturation detection methods of state can refer to the " transformer based on Mathematical Morphology gradient that Zheng Tao, Gu Jun, the few cutting edge of a knife or a sword of Huang etc. are delivered
Evolved fault identifies new criterion " (Proceedings of the CSEE, 2008,28 (22):75-80) etc..In addition to the method described above,
Detection of the methods of domestic and foreign scholars are also by based on small vector technology, correlation analysis applied to CT saturations, can refer to Deng Xiangli, king
Biography opens, " the fast differential current quick based on small vector technology " that wise man etc. delivers (Automation of Electric Systems, 2012,
36(14):67-71).These methods all solve the problems, such as CT saturation detections to a certain extent, but still remain very much
Limitation and deficiency, therefore, continue to deepen very necessary to the research and development of CT saturation detection methods.
Invention content
The purpose of the present invention is being directed to, previous CT saturation detection algorithms precision that may be present is low, detection speed is slow, algorithm
The problems such as complicated, a kind of CT saturation detection method based on current waveform area accounting of proposition.
It is of the invention specifically to use following technical scheme.
A kind of CT saturation detection method based on waveform area accounting method, it is characterised in that：It will sampling gained
Practical saturation secondary current waveform normalized on the basis of maximum value, calculate practical saturation secondary current waveform and time
The area that axis surrounds, according to the area that practical saturation secondary current waveform and time shaft surround and preferable secondary current waveform and when
The area ratio that countershaft surrounds judge CT occur saturation light and heavy degree.
A kind of CT saturation detection method based on waveform area accounting method, which is characterized in that the method packet
Include following steps：
(1) standard sine current waveform is defined, i.e. maximum value is 1, period 20ms, referred to as ideal normalization secondary current
Waveform；Its area is calculated as definite value S1=6.3629；
(2) secondary side current of current transformer to be detected is sampled first；
(3) the first of secondary current cycle that step (2) is detected is taken, to practical secondary side current with step (1)
Defined in maximum value 1 on the basis of be normalized, to the secondary current waveform after normalized about time shaft accumulate
Point, calculate to obtain its area S2；
(4) represent one cycle of actual samples secondary current to time shaft institute envelope surface product and preferable secondary current one with DR
Cycle encloses time shaft area ratio S2/S1,
When DR is less than 0.9, i.e. being considered as current transformer has occurred saturation, and numerical value is smaller, and saturation is more serious；When DR is more than
0.9, it can be considered that current transformer works normally.
Beneficial effects of the present invention：
A kind of CT saturation detection method based on current waveform area accounting proposed by the invention, emphasis solution
Detection speed and accuracy of detection problem during current transformer of having determined generation saturation.Area accounting method efficiently utilizes CT saturations
When secondary current can not correctly the progress of disease primary current the characteristics of, show primary current have more regular sine wave shape,
Preferable secondary current waveform after the progress of disease also should be sine wave, and after the secondary current of saturation is distorted, there is waveform
Interruption, distortion, bending phenomenon.Thus it is different from the area that time shaft is surrounded.This method can be just with a cycle
Or half of cycle just can reach testing goal, greatly reduce in electric system since CT saturations cause protective relaying device to miss
Dynamic or tripping possibility.With regard to that can detect saturation within the extremely short time, so as to send out the signal of latch-up protection, also avoid
Malfunction caused by external area error CT saturations in the protection of transformer difference stream.Meanwhile area accounting method has very high precision, it is right
It is less saturated in CT, to correct action is protected to have little effect；And during more serious saturation, saturation secondary current with it is preferable
Secondary current area accounting DR is generally much smaller than 0.9, and high sensitivity ensure that the correctness of saturation detection.This is relative to other
Detection method is unstable, in terms of the low advantage of precision.Finally, this method principle is simple, realization is easily programmed, to hardware and software
Requirement it is all very low.Therefore a kind of CT saturation detection method based on current waveform area accounting is protected to improving relay
The stability that nurse makees, it is ensured that quick and precisely action has important practical meaning in engineering for protection.
Description of the drawings
Fig. 1 is current transformer equivalent circuit diagram；
Fig. 2 is simulation flowchart system for use in carrying simulation model；
Fig. 3 for current transformer it is less saturated when ideal is secondary, saturation secondary current waveform；
Ideal is secondary when Fig. 4 is current transformer moderate saturation, saturation secondary current waveform；
Ideal is secondary when Fig. 5 is current transformer severe saturation, saturation secondary current waveform；
Fig. 6 is the CT saturation detection method flow chart proposed by the present invention based on waveform area accounting method.
Specific embodiment
With reference to the accompanying drawings of the specification and specific embodiment is further described in detail technical scheme of the present invention.
The present invention proposes a kind of CT saturation detection method based on current waveform area accounting, with reference to attached
Figure is explained.
Using Fig. 1 current transformer equivalent models, i1Expression flows through the primary current of system, i2For Current Transformer Secondary
Side electric current, imFor exciting current, Zm is excitation impedance, R2, L2For secondary winding resistance and inductance.Using MATLAB simulation softwares,
Electric power system model shown in Fig. 2 is built, is bilateral source single system, both sides power phase is inconsistent, and electric current is built in side
Mutual inductor sets short trouble on circuit.After simulated failure occurs, take CT that first all wave analysis after saturation occurs.
A kind of such as Fig. 6 flows of the CT saturation detection method based on current waveform area accounting disclosed by the invention
Shown in figure.Detection method includes the following steps：
1) standard sine current waveform is defined, i.e. maximum value is 1, period 20ms, samples per cycle at 80 points, the sampling interval
For 0.25ms, referred to as preferable normalization secondary current waveform.Its area is calculated as definite value S1=6.3629.
2) secondary side current of current transformer is sampled first, 80 sampled point analyses is taken to calculate per cycle.
3) the first of secondary current cycle that step (2) is detected is taken, to practical secondary side current in step (1)
It is normalized on the basis of the maximum value 1 of definition, that is, takes the maximum value of first cycle of actual current waveform, with step
(1) Plays sinusoidal current waveform maximum value 1 is compared to amplification factor is obtained, by actual current waveform sample values according to amplification factor
Normalization.For practical secondary current waveform after normalization as former practical secondary current waveform shape, amplitude is different.To returning
One changes treated secondary current waveform integrates about time shaft, calculates to obtain its area S2.
4) represent one cycle of actual samples secondary current to time shaft institute envelope surface product and preferable secondary current one with DR
Cycle encloses time shaft area ratio, i.e.,
When DR is less than 0.9, i.e. being considered as current transformer has occurred saturation, and numerical value is smaller, and saturation is more serious；When DR is more than
0.9, it can be considered that current transformer works normally.
Technical scheme of the present invention is introduced in conjunction with specific embodiments further below：
For electric power system model shown in Fig. 2, to CT saturations using waveform area accounting method to slight, moderate, severe three
Kind situation carries out simulation calculation verification：
1st, added both sides power supply is respectively S1, and S2, CT no-load voltage ratios are 2000：5, circuit overall length 200Km set different failures
Position, CT secondary loads and remanent magnetism situation are obtained such as Fig. 3,4,5 three kinds of saturated conditions, reason when Fig. 3 occurs less saturated for CT
Think secondary current and practical secondary current waveform, it is seen that practical secondary current wave distortion degree is low, with preferable secondary current wave
Shape similarity is higher；Fig. 4,5 be respectively preferable secondary current and practical secondary current waveform under moderate and severe saturated conditions
Figure, it can be seen that degree of saturation is deeper, and practical secondary current wave distortion degree is bigger, bigger with preferable secondary current difference；
2nd, saturation secondary current waveform area S2 under slight, moderate, severe saturation is calculated, only takes an identical cycle
Interior data calculate integral area；
3rd, by gained area value be calculated respectively it is corresponding in the case of DR values, respectively 0.8987,0.5636,
0.1961, it is as shown in the table；
| Slight saturation | Moderate saturation | Severe saturation | |
| Saturation secondary current waveform area S2 | 5.7184 | 3.5861 | 1.2478 |
| Preferable secondary current waveform area S1 | 6.3629 | 6.3629 | 6.3629 |
| Area accounting DR | 0.8987 | 0.5636 | 0.1961 |
Therefore for slight saturation, general electric system is defaulted as unsaturation, i.e., does not have to the normal operation of equipment and system
Have an impact, the definite value that especially DR values can make CT generation saturations is 0.9, if DR is less than 0.9, is judged to that saturation has occurred；DR is big
In 0.9, saturated phenomenon does not occur.
Applicant combines Figure of description and table is described in detail and describes to the embodiment of the present invention, still
It should be appreciated by those skilled in the art that each fault message fractional value and influence factor correction factor are only this in above example
The preferred embodiment of invention, those skilled in the art's entirely possible specific generator of basis under the invention thought of the present invention
Group excitation system model and actual condition fault message fractional value and influence factor correction factor are carried out reasonably selection or
Modification.In short, explanation is intended merely to that reader is helped to more fully understand spirit of the invention the application in detail, and not to the present invention
The limitation of protection domain, on the contrary, any improvement or modification that any spirit based on the present invention is made should be all fallen at this
Within the protection domain of invention.
Claims (1)
1. a kind of CT saturation detection method based on waveform area accounting method, which is characterized in that the method includes
Following steps：
(1) standard sine current waveform is defined, i.e. maximum value is 1, period 20ms, referred to as ideal normalization secondary current wave
Shape；Its area is calculated as definite value S1=6.3629；
(2) secondary side current of current transformer to be detected is sampled first；
(3) the first of secondary current cycle that step (2) is detected is taken, to practical secondary side current with fixed in step (1)
It is normalized, the secondary current waveform after normalized is integrated about time shaft, meter on the basis of the maximum value 1 of justice
Calculate to obtain its area S2；
(4) represent one cycle of actual samples secondary current to time shaft institute envelope surface product and one cycle of preferable secondary current with DR
Area ratio S2/S1 is enclosed to time shaft,
When DR is less than 0.9, i.e. being considered as current transformer has occurred saturation, and numerical value is smaller, and saturation is more serious；When DR be more than 0.9, can
It is considered as current transformer normal work.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104810796B (en) * | 2015-04-30 | 2018-02-13 | 国家电网公司 | Excitation surge current discrimination method based on variable data window normalized area index |
| CN105552834B (en) * | 2015-12-30 | 2018-05-11 | 华自科技股份有限公司 | The method and system of the anti-CT saturations of current differential protection |
| CN106371047B (en) * | 2016-08-17 | 2018-09-11 | 云南电网有限责任公司电力科学研究院 | A kind of saturation determination method of low-power iron-core coil current transformer |
| CN106932747B (en) * | 2017-05-08 | 2019-08-13 | 中国南方电网有限责任公司 | A kind of CT saturation detection method that global and local feature combines |
| CN107340489B (en) * | 2017-07-05 | 2019-10-08 | 广东电网有限责任公司电力科学研究院 | A kind of CT saturation detection method and device |
| CN110208596B (en) * | 2019-05-16 | 2021-03-30 | 深圳和而泰小家电智能科技有限公司 | Load current monitoring circuit and method |
| CN111308406A (en) * | 2020-04-07 | 2020-06-19 | 国网江苏省电力有限公司电力科学研究院 | Current transformer saturation detection method, system, medium and electronic equipment |
| CN115566651B (en) * | 2022-10-25 | 2023-06-02 | 上海山源电子科技股份有限公司 | Coal mine power supply quick-break protection method based on CT saturation judgment |
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| JP2997495B2 (en) * | 1990-03-16 | 2000-01-11 | 同和鉱業株式会社 | Magnetic flux focusing method and apparatus |
| JP2003329722A (en) * | 2002-05-15 | 2003-11-19 | Mitsubishi Electric Corp | Failure-point locating apparatus |
| CN1635679B (en) * | 2003-12-30 | 2010-12-15 | 许继电气股份有限公司 | Method of current transformer saturation identification and method of current differential protection on saturation thereof |
| CN101046500A (en) * | 2007-04-23 | 2007-10-03 | 国电南京自动化股份有限公司 | Current transformer saturation detecting technology based on correlation coefficient process |
| CN103529321B (en) * | 2013-10-10 | 2016-01-20 | 长园深瑞继保自动化有限公司 | CT saturation detection method |
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