CN102288804B - Method for calculating resistive current of arrester based on orthogonal transformation - Google Patents
Method for calculating resistive current of arrester based on orthogonal transformation Download PDFInfo
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- CN102288804B CN102288804B CN201110203554.8A CN201110203554A CN102288804B CN 102288804 B CN102288804 B CN 102288804B CN 201110203554 A CN201110203554 A CN 201110203554A CN 102288804 B CN102288804 B CN 102288804B
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Abstract
The invention discloses a method for calculating resistive current of an arrester based on orthogonal transformation. The method comprises the following steps of: defining I<c><&>, I<r><&>, I<&>, and U<c><&> respectively representing a capacitive current vector value, a resistive current vector value, a full current vector value and a voltage vector value, i(t)=sqrt(2)*Icos(2pif0t+phi); and if no harmonic component is present, adopting an algorithm which comprises the following substeps of: 1) performing discrete sampling on i(t) to obtain a formula (1); 2) constructing a reference signal to obtain a formula (2); 3) multiplying the formula (1) by the formula (2) to obtain a formula (3); 4) solving a phase value of the formula (3); and 5) calculating the resistive current; and if the harmonic component is present or power frequency has deviation, correcting the 1) and 2) in the step 2. In the algorithm, only a full current signal is needed, a full voltage signal and other extra conditions are not needed, the resistive current can be solved, and the cost is reduced; moreover, harmonic and noise interference can be effectively suppressed, and the precision is improved.
Description
Technical field
The present invention relates to a kind of computing method, specifically arrester resistance current computing method.
Background technology
Lightning arrester is as the important component part of electric equipment protection device in high-voltage fence, and the monitoring of himself performance is also to guarantee one of key factor of the normal work of power equipment.At present, lightning arrester performance monitoring mainly relies on the resistive component measurement in its leakage current (or claiming total current) is carried out.Under normal circumstances, resistive current weight is the circuital 5-20% of some left and right approximately, and its order of magnitude is microampere order, therefore, directly measures comparatively difficulty of current in resistance property.From the quantitative relation between current in resistance property and total current and capacity current, measuring phase differential between resistive component and total current is the key link of calculating arrester resistance current.
Prior art is mainly calculated by following two kinds of methods: one, total current full voltage method: by PT sensor, measure respectively total current and full voltage, calculate phase differential between the two, because the phase place of current in resistance property is identical with full voltage phase place, therefore the total current calculating is identical with the phase differential of total current and current in resistance property with the phase differential of full voltage, so just can calculate current in resistance property value.The shortcoming of this method is to need PT sensor, and total current and full voltage amount need two to overlap independently measuring system, may introduce more multiple error, is subject to the impact of harmonic wave, external disturbance and noise larger, and cost is also larger simultaneously.Two, total current method: this method only needs to measure total current, then by finding first zero crossing of full current waveform, reconstruct the waveform of capacity current, after the capacitive component in total current is removed, obtain current in resistance property value.The shortcoming of this method is to carry out zero passage detection, so it detects the impact that performance must be subject to the waveform variations that causes because of the humorous impact that involves noise.
Summary of the invention
The object of the invention is the deficiency existing for prior art, providing a kind of only needs full current signal without other subsidiary condition and can suppress the humorous arrester resistance current computing method based on orthogonal transformation that involve noise.
For achieving the above object, the technical solution used in the present invention is a kind of arrester resistance current computing method based on orthogonal transformation, comprises the following steps:
One, first definition
the phasor value that represents respectively capacity current vector value, current in resistance property vector value, total current vector value and voltage, order
in formula, I represents the effective value of full power supply, f
0for power frequency 50Hz,
for initial phase;
Two, make j represent imaginary unit, y (n) is the intermediate variable of introducing, and i (n) is the sequence of total current after discrete sampling, and Δ t represents sampling interval, and AVER (x) represents to average;
If three when exist without harmonic component, algorithm is as follows:
1) i (t) is carried out to discrete sampling, obtain
and carry out orthogonal transformation, obtain the analytic signal form of i (n)
2) structure reference signal
3) formula (1) and formula (2) are multiplied each other, obtain
4) ask for the phase value of formula (3)
5) calculate current in resistance property:
If four exist harmonic component, or work frequency is while having deviation, in step 2 1), 2) do to revise as follows:
1) total current completes after discrete sampling, when doing orthogonal transformation, and filtering 3 times and more higher harmonic components;
2) power frequency has deviation, is regarded as unknown frequency signal, utilizes frequency estimating methods, recycling frequency estimation, structure reference signal.
Beneficial effect: this algorithm of the present invention only needs full current signal, without full voltage signal and other additional condition, just can ask for current in resistance property, has reduced cost, and can effectively suppress the humorous interference that involves noise, has improved precision.
Accompanying drawing explanation
Fig. 1 is the equivalent-circuit model that total current of the present invention is measured;
Fig. 2 is the schematic diagram that is related between each amount of the present invention;
Fig. 3 is the total current simulation waveform (work frequency is 49.5Hz) while having harmonic component.
Embodiment
Below in conjunction with the drawings and specific embodiments, further illustrate the present invention, the present embodiment is implemented take technical solution of the present invention under prerequisite, should understand these embodiment and only for the present invention is described, is not used in and limits the scope of the invention.
Arrester resistance current computing method based on orthogonal transformation, comprise the following steps:
One, first definition
the phasor value that represents respectively capacity current vector value, current in resistance property vector value, total current vector value and voltage, order
in formula, I represents the effective value of full power supply, f
0for power frequency 50Hz,
for initial phase;
Two, make j represent imaginary unit, y (n) is the intermediate variable of introducing, and i (n) is the sequence of total current after discrete sampling, and Δ t represents sampling interval, and AVER (x) represents to average;
If three when exist without harmonic component, algorithm is as follows:
1) i (t) is carried out to discrete sampling, obtain
and carry out orthogonal transformation, obtain the analytic signal form of i (n)
2) structure reference signal
3) formula (1) and formula (2) are multiplied each other, obtain
4) ask for the phase value of formula (3)
5) calculate current in resistance property:
If four exist harmonic component, or work frequency is while having deviation, in step 2 1), 2) do to revise as follows:
1) total current completes after discrete sampling, when doing orthogonal transformation, and filtering 3 times and more higher harmonic components;
2) power frequency has deviation, is regarded as unknown frequency signal, utilizes frequency estimating methods, recycling frequency estimation, structure reference signal.
According to the total current model of recommending in the power industry standard DLT985-2005 < < of People's Republic of China (PRC) zinc oxide lightning arrester block property current tester test condition > >, the model of establishing full current signal is
i(t)＝I
r1cos(2πf
0t)+I
r3cos(6πf
0t+π)+I
c1cos(2πf
0t+π/2)
I in formula
r1represent resistive current first harmonics component maximal value, I
r3the maximal value that represents current in resistance property third-harmonic component, I
c1the first-harmonic maximal value that represents capacitive current component.For the stochastic error of analog meter, below in two routine emulation, the zero-mean that superposeed in the full current signal of supposing, variance is the white Gaussian noise of total current maximal value 0.05%.
Example one: while existing without harmonic component, algorithm simulating during power frequency fluctuation;
During without harmonic component, second of above-mentioned universal model is zero, now only has the fundametal compoment of current in resistance property and the fundametal compoment of capacity current.Suppose without power frequency error, I
r1=156.4 μ A, I
c1=987.7 μ A, the sampling time of full current signal is 40ms, sample frequency is 3.2KHz.In the 49.5Hz to 50.5Hz that work frequency allows in electric system, fluctuate, frequency change step-length 0.1Hz, makes 100 times Monte Carlo simulation under every kind of frequency, calculates average and standard deviation that current in resistance property is measured.Its simulation results is as listed in table 1.
Table 1 is for there being while fluctuation current in resistance property emulation testing performance without harmonic wave power frequency
| Power frequency (Hz) | Mean value (uA) | Root-mean-square error (uA) |
| 50.5 | 158.0213533 | 1.766503443 |
| 50.4 | 157.9879399 | 1.734651178 |
| 50.3 | 157.1770409 | 0.947842542 |
| 50.2 | 157.3058868 | 0.994225698 |
| 50.1 | 157.6372247 | 1.448310733 |
| 50 | 158.4320164 | 2.279156885 |
| 49.9 | 158.7511606 | 2.57016704 |
| 49.8 | 158.1824119 | 1.81960506 |
| 49.7 | 158.018421 | 1.673909288 |
| 49.6 | 159.090167 | 2.809691782 |
| 49.5 | 158.8889467 | 2.628828846 |
By table 1, during as seen without harmonic wave, there is certain fluctuation in power frequency, and the accuracy in computation of current in resistance property is still higher.
Example two: the algorithm while there is harmonic component, simulation calculation example when power frequency exists fluctuation; Suppose that third-harmonic component is 1/3 of fundametal compoment, other emulation testing condition is still identical with example two.Figure 3 shows that total current simulation waveform when work frequency is 49.5Hz.The simulation results obtaining is as listed in table 2.
Table 2 is for there being harmonic wave power frequency to have while fluctuation current in resistance property emulation testing performance
| Power frequency (Hz) | Mean value (uA) | Root-mean-square error (uA) |
| 50.5 | 157.1410885 | 1.065268923 |
| 50.4 | 156.7504072 | 0.533091875 |
| 50.3 | 156.2621368 | 0.699928292 |
| 50.2 | 157.6664364 | 1.685290395 |
| 50.1 | 157.38338 | 1.26499 |
| 50 | 159.0173026 | 2.885083644 |
| 49.9 | 157.6291791 | 1.327607541 |
| 49.8 | 160.0598857 | 3.831735337 |
| 49.7 | 159.6739497 | 3.345139911 |
| 49.6 | 161.3503688 | 5.057250502 |
| 49.5 | 161.974519 | 5.750353722 |
By table 1, table 2 is known: during without harmonic wave, the true value ratio of the mutually resistive current maxima of root-mean-square error of the current in resistance property that this method calculates is less than 1%; While having harmonic wave, this ratio is less than 3.6%, and this precision meets the power industry standard DLT985-2005 < < of People's Republic of China (PRC) zinc oxide lightning arrester block property current tester test condition > > and requires.Obviously, the precision of measurement is also subject to concrete sample of signal length, the impact of the factors such as the random superposition noise of waveform.
Claims (1)
1. arrester resistance current computing method based on orthogonal transformation, is characterized in that comprising the following steps:
One, first definition
the phasor value that represents respectively capacity current vector value, current in resistance property vector value, total current vector value and voltage, makes circuital instantaneous value be
in formula: I represents circuital effective value, f
0for power frequency 50Hz,
for initial phase, t is time variable;
Two, make j represent imaginary unit, y (n) is the intermediate variable of introducing, and i (n) is the sequence of total current after discrete sampling, and Δ t represents sampling interval, and AVER (x) represents to average;
If three when exist without harmonic component, algorithm is as follows:
1) i (t) is carried out to discrete sampling, obtain
and carry out orthogonal transformation, obtain the analytic signal form of i (n)
2) structure reference signal
3) formula (1) and formula (2) are multiplied each other, obtain
4) ask for the phase value of formula (3)
5) calculate current in resistance property:
If four exist harmonic component, or work frequency is while having deviation, in step 3 1), 2) do to revise as follows:
1) total current completes after discrete sampling, when doing orthogonal transformation, and filtering 3 times and more higher harmonic components;
2) power frequency has deviation, is regarded as unknown frequency signal, utilizes frequency estimating methods, recycling frequency estimation, structure reference signal;
Described step 3 1) in, orthogonal transformation realizes by quick Fu's formula conversion FFT;
Described step 4 2) medium frequency method of estimation is RIFE algorithm.
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| CN102841252B (en) * | 2012-09-07 | 2015-09-30 | 上海电力学院 | The quick detection of passband type single phase alternating current power supply first-harmonic and harmonic wave and computing method |
| CN103207308B (en) * | 2013-03-13 | 2015-08-26 | 福建省电力有限公司 | The measuring method of arrester resistance current and capacity current transient value |
| CN104459296B (en) * | 2013-11-27 | 2017-10-13 | 南京世都科技有限公司 | A kind of method and device based on the relatively quasi- current in resistance property measurement of the positive inverse transformations of Fourier FFT |
| CN104459297B (en) * | 2013-11-27 | 2017-10-13 | 南京世都科技有限公司 | A kind of utilization double frequency transmission and the system measured based on the positive inverse transformation calibration current in resistance property of Fourier FFT |
| CN104330615B (en) * | 2014-10-31 | 2018-12-14 | 南京世都科技有限公司 | The how identical survey devices and methods therefor of arrester and transformer based on fft algorithm |
| CN105467209B (en) * | 2015-12-02 | 2018-06-29 | 国网四川省电力公司资阳供电公司 | A kind of new metal oxide arrester leakage current analysis method |
| CN106018998B (en) * | 2016-05-12 | 2018-12-14 | 广东电网有限责任公司电力科学研究院 | A kind of arrester test method and system |
| CN108256153B (en) * | 2017-12-20 | 2023-12-22 | 中国电力科学研究院有限公司 | Lightning arrester-based electromechanical transient simulation modeling method and system |
| CN115575856B (en) * | 2022-11-18 | 2023-03-07 | 国网四川省电力公司成都供电公司 | Online monitoring method and system for leakage current of lightning arrester in power transmission cable terminal field |
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| CN101726675A (en) * | 2008-10-28 | 2010-06-09 | 武汉华瑞测控科技有限公司 | Method for performing live-line evaluation on online insulation monitoring system of substation |
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| JP2000284013A (en) * | 1999-03-29 | 2000-10-13 | Sho Minamiyama | Device for detecting and displaying degradation of zinc oxide-type lightening arrester and method for detecting degraded component |
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| CN101726675A (en) * | 2008-10-28 | 2010-06-09 | 武汉华瑞测控科技有限公司 | Method for performing live-line evaluation on online insulation monitoring system of substation |
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