CN105467209B - A kind of new metal oxide arrester leakage current analysis method - Google Patents
A kind of new metal oxide arrester leakage current analysis method Download PDFInfo
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- CN105467209B CN105467209B CN201510867737.8A CN201510867737A CN105467209B CN 105467209 B CN105467209 B CN 105467209B CN 201510867737 A CN201510867737 A CN 201510867737A CN 105467209 B CN105467209 B CN 105467209B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R25/00—Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
Abstract
The invention discloses a kind of new metal oxide arrester leakage current analysis method, first to the dis-crete sample values of power network signalMeet 10 cycle adding window as defined in IEC standard, Hanning windows are added when performing asynchronous, then the spectrum value at spectral line k is corresponded to after DFT/FFT is convertedSpectrum value is multiplied by the rotatable phase factor twiceThe amplitude at frequency point obtained after transformation is vector superposed, to obtain the frequency of arrester, amplitude and the exact value of phase parameter.The analysis method converted by twiddle factor after frequency point at amplitude it is vector superposed can be eliminated in fundamental frequency non-synchronous sampling fence effect and inhibit spectrum leakage, the influence that instantaneous big interference fringe comes is eliminated simultaneously, avoids the mistake that traditional FFT algorithm detects appearance under non-synchronous sampling or instantaneous big interference cases.
Description
Technical field
The present invention relates to leakage current of an arrester analysis fields, and in particular to a kind of new metal oxide arrester leakage
Amperometry method.
Background technology
By the study found that the change of the operating status of arrester, which is embodied in, flows through the total current and current in resistance property of arrester
The change of the two inner parameters, you can to characterize the operation shape of practical arrester with the total current and current in resistance property of arrester
State realizes monitoring and early warning during arrester operation.
Analysis for voltage, current signal in the circuit of the arrester containing connection, it is necessary first to accurately be surveyed to it
Amount.Theoretically voltage signal contains only fundamental signal, and current signal is also containing 3 times, 5 inferior harmonic waves in addition to fundamental signal
Signal, traditional fft algorithm are suitable for strong signal, the situation of small interference, do not have theoretical error in fundamental frequency synchronized sampling, for
Voltage, the result of electric current are more accurate.And voltage, current signal in actual circuit it is possible that problems with and cause to pass
Fft algorithm detection of uniting is failed：1) spectrum leakage and fence effect problem that fundamental frequency non-synchronous sampling is brought, due to power grid fundamental wave frequency
The rate moment be in fluctuation among, maximum fluctuation range within ± 0.5Hz, normal fluctuation situation within ± 0.2Hz, and by
The error that this brings is larger, and phase error is likely to be breached 5 ° or more, and subsequent calculating is caused serious error occur；2) due to electricity
Contain arrester in road, therefore voltage, current signal may bear the high frequency from thunder and lightning signal and instantaneously interfere greatly, and hardware
Frequency overlapped-resistable filter is likely to occur that signal attenuation is not thorough or big interfering frequency is less than the cutoff frequency of frequency overlapped-resistable filter
Situation, big interference at this time have a very big impact the detection of voltage, current signal.For voltage, current signal it is high-precision
Degree measures, and it is crucial to solve problem above.
Invention content
The present invention overcomes the deficiencies in the prior art, provide a kind of new metal oxide arrester leakage current analysis side
Method, the amplitude at frequency point after being converted by twiddle factor is vector superposed to eliminate fence effect in fundamental frequency non-synchronous sampling
With inhibit spectrum leakage, while eliminate the influence that instantaneous big interference fringe comes, avoid traditional FFT algorithm in non-synchronous sampling or wink
When big interference cases under detect the mistake of appearance.
The present invention uses following technical scheme：
A kind of new metal oxide arrester leakage current analysis method, which is characterized in that first to power network signal
Dis-crete sample valuesMeet 10 cycle adding windows as defined in IEC standard,
Add Hanning windows when performing asynchronous, then the spectrum value at spectral line k is corresponded to after DFT/FFT is convertedSpectrum value is once multiplied by the rotatable phase factorIt is superimposed againTransformation obtains new frequency spectrum informationAgain by new frequency spectrumPhase
Adjacent spectral line, which is added, eliminates secondary lobe superposition leakage, then the 3 spectral line ratio formula based on twiddle factor, spectrum value formula in conjunction with
Hanning windowsThe anti-frequency offseting value for solving 3 spectral line interpolations：
Construct three spectral lines further according to three spectral lines and relational expression
And frequency spectrumSidelobe performance calculated rate, amplitude and phase value, wherein Δ t are the unit sampling interval, and M is component number,
fi、Ai、For the frequency, amplitude and phase of component, n=0,1 ..., N-1, N be sampling window length, βi=fi/ Δ f is unit
Change frequency values, corresponding frequency resolution when Δ f is sample window a length of N, W () represents the window spectral function of corresponding adding window, as N ＞
The expression formula that Hanning window spectral functions are corresponded to during ＞ 1 is as follows：
The 3 spectral line ratio formula based on twiddle factor areWherein ki、For respective frequencies component fiMaximum
Spectral line serial number and frequency offseting value, and After expression multiplies the rotatable phase factor
Remaining component is to component f on frequency spectrumiSecondary lobe interference superposition value.
The formula for specifically calculating accurate frequency is：Wherein ki、For respective frequencies
Component fiMaximum spectral line serial number and frequency offseting value, and
Specifically calculating accurate amplitude formula is
The formula for specifically calculating accurate phase parameter is
Compared with prior art, the beneficial effects of the invention are as follows：
The present invention eliminates the intrinsic fence effects and spectrum leakage of FFT by the spectral line vector addition interpolation at multifrequency point
It influences, while counteracts big interference of the interference to spectrum signal of instantaneous high frequency, so as to accurately measure voltage, electric current
Amplitude, frequency and phase parameter so that final parameters precision improves.
Description of the drawings
Fig. 1 changes twiddle factor to offset leakage schematic diagram；
DFT fence effects and spectrum leakage phenomenon during Fig. 2 fundamental frequency non-synchronous samplings；
The signal time-domain diagram of Fig. 3 big interference containing instantaneous high frequency；
The signal spectrum figure of Fig. 4 big interference containing instantaneous high frequency.
Specific embodiment
The invention will be further elaborated below in conjunction with the accompanying drawings.
Embodiment 1
To sampled data meet as defined in IEC standard 10 cycle adding windows, (fundamental frequency adds rectangular window, asynchronous when synchronizing
When add Hanning windows) DFT/FFT spectrum analyses obtain spectrum information.
Dis-crete sample values for power network signal are：
In formula Δ t be the unit sampling interval, M be component number, fi、Ai、For the frequency, amplitude and phase of component, n=
0th, 1 ..., N-1, N are sampling window length.
The spectrum value that corresponds at spectral line k is after formula (1) carries out DFT/FFT transformation：
β in formulai=fi/ Δ f is unit frequency values, corresponding frequency resolution when Δ f is sample window a length of N, W ()
Represent the window spectral function of corresponding adding window, the expression formula that Hanning window spectral functions are corresponded to as N ＞ ＞ 1 is as follows：
Above-mentioned frequency spectrum is carried out to multiply the rotatable phase factorHandle to obtain new frequency spectrum informationCause each component master
Phase in valve is exactly the same, and the phase in secondary lobe is stringent on the contrary, amplitude is close.
Formula (2) is expressed as：
Contain in the phase factor of formula intermediate frequency spectrum G (k) componentsTwo, with spectrum
The difference of line position and change, be affected when k values are larger, in order to which the phase value in formula (4) is not with the variation of position of spectral line k
And change, it is multiplied by the rotatable phase factorTo offset its variation, i.e.,：
By unitization frequency values βiIt is written as form：
Wherein ki、For respective frequencies component fiMaximum spectral line serial number and frequency offseting value, and
Formula (5) is expressed as：
I.e.
WhereinExpression multiplies after the rotatable phase factor on frequency spectrum remaining component to component fiSide
Valve interferes superposition value, to single value Δ (km) for, secondary lobe amplitude is close, phase directional is strictly opposite.
It is as shown in Figure 1 to offset the schematic diagram of leakage thought that it changes twiddle factor.
By to new frequency spectrumAdjacent spectral line is added the thought to eliminate part secondary lobe superposition leakage, can be by adjacent
The corresponding spectrum value phase Calais of spectral line inhibits secondary lobe leakage contribution of other components to concern component, i.e. Δ (ki)+Δ(ki-1)≈
0、Δ(ki)+Δ(ki+ 1) ≈ 0, then
So, the 3 spectral line ratios based on twiddle factor are：
Have for Hanning windowsFormula (11) abbreviation is：
The anti-frequency offseting value for solving 3 spectral line interpolations：
Therefore, the frequency values for paying close attention to component are：
It is constructed using three spectral lines：
According to frequency spectrumSidelobe performance, [Δ (ki-1)+2Δ(ki)+Δ(ki+ 1)] ＜ ＜ Δs (ki), then formula (15) is changed
Letter is：
Have for Hanning adding windows：
Formula (16) is converted into：
Therefore
WhereinAngle () represents to return to corresponding angle value, formula (14) (19)
(20) it is to be derived most based on the multifrequency point interpolation fourier algorithm (abbreviation multifrequency point interpolation algorithm) that twiddle factor converts
Whole calculation formula compares frequency, amplitude and the initial phase of institute's signal Analysis fundamental wave and harmonic wave respectively.
The fence effect and spectrum leakage phenomenon generated during fundamental frequency non-synchronous sampling is as shown in Figure 2：
If sample frequency fs=12800Hz, sampling cycle are Mt=10 cycle, are N=2560 per cycle sampling number
Point, fundamental frequency 50Hz, each harmonic theoretical value is as shown in table 1, while is superimposed the white Gaussian noise that signal-to-noise ratio is 20dB, separately
The outer random instantaneous big interference of high frequency of superposition, amplitude are 10 times of fundamental voltage amplitude, duration 1ms.
1 each harmonic wave m-Acetyl chlorophosphonazo parameter theory value of table
Time and frequency domain analysis is carried out to above-mentioned signal, obtains signal time-domain diagram and spectrogram respectively as shown in Figure 3 and Figure 4.
Utilize the comparison of the measuring result error of carried multifrequency point interpolation algorithm and traditional FFT algorithm as shown in table 2.
2 multifrequency point interpolation algorithm of table and traditional FFT algorithm measurement error
From table 2 it can be seen that traditional FFT algorithm containing instantaneous high frequency it is big interference, fundamental frequency non-synchronous sampling when, due to by
To the influence of fence effect and spectrum leakage, frequency error, amplitude error in testing result, phase error are all bigger,
Phase error therein has been more than 5 ° so that fails to the higher occasion of phase measurement exact requirements, while instantaneous high frequency is big
It interferes and is affected to normal measure of parameter, result is caused larger error occur；The multifrequency point interpolation algorithm carried can be with
Accurately measure voltage, the amplitude of electric current, frequency and phase parameter, can particularly meet in this project to the high-precision of phase
Testing requirements are spent, the intrinsic fence effects of FFT and spectrum leakage shadow are eliminated by the spectral line vector addition interpolation at multifrequency point
It rings, while counteracts interference of the big interference of instantaneous high frequency to spectrum signal so that final parameters precision improves.
Measured data is verified：
Sample same arrester two voltage in different time periods, current data, voltage, electric current wherein in a period of time
Oscillogram is illustrated in fig. 5 shown below.
In order to carry out the measurement of follow-up arrester resistance current, accurately extraction electric current, voltage phase difference are crucial, using biography
System FFT and multifrequency point interpolation method carry out phase difference measurement comparison, and the results are shown in Table 3：
3 measured data analysis result of table
Table 3 shows that practical fundamental frequency has subtle offset 50Hz, and there are certain harmonic wave and disturbances in signal in addition
Interference so that traditional FFT method has larger deviation when measuring phase difference, and multifrequency point interpolation method eliminates fence effect
With inhibit spectrum leakage, therefore the phase difference deviation measured is smaller, can meet actual requirement of engineering.
Claims (4)
1. a kind of new metal oxide arrester leakage current analysis method, which is characterized in that first to power network signal from
Dissipate sampled valueMeet 10 cycle adding windows as defined in IEC standard, hold
Row adds Hanning windows, then the spectrum value at spectral line k is corresponded to after DFT/FFT is converted when asynchronousSpectrum value is once multiplied by the rotatable phase factorIt is superimposed againTransformation obtains new frequency spectrum informationAgain by new frequency spectrumPhase
Adjacent spectral line, which is added, eliminates secondary lobe superposition leakage, then the 3 spectral line ratio formula based on twiddle factor, spectrum value formula in conjunction with
Hanning windowsThe anti-frequency offseting value for solving 3 spectral line interpolations：
Construct three spectral lines further according to three spectral lines and relational expression and
Frequency spectrumSidelobe performance calculated rate, amplitude and phase value, wherein Δ t be the unit sampling interval, M be component number, fi、
Ai、For the frequency, amplitude and phase of component, n=0,1 ..., N-1, N be sampling window length, βi=fi/ Δ f is unit
Frequency values, corresponding frequency resolution when Δ f is sample window a length of N, W () represents the window spectral function of corresponding adding window, as N ＞ ＞
The expression formula that Hanning window spectral functions are corresponded to when 1 is as follows：
The 3 spectral line ratio formula based on twiddle factor areWherein ki、For respective frequencies component fiMaximum
Spectral line serial number and frequency offseting value, and After expression multiplies the rotatable phase factor
Remaining component is to component f on frequency spectrumiSecondary lobe interference superposition value.
2. analysis method according to claim 1, it is characterised in that：The formula for specifically calculating accurate frequency is：
Wherein ki、For respective frequencies component fiMaximum spectral line serial number and frequency shift (FS)
Value, and
3. analysis method according to claim 1, it is characterised in that：Specifically calculating accurate amplitude formula is
4. analysis method according to claim 1, it is characterised in that：The formula for specifically calculating accurate phase parameter is
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| CN109239518B (en) * | 2018-10-29 | 2021-08-06 | 河北工业大学 | Fault leakage current detection method for variable frequency speed control system |
| CN109557355A (en) * | 2018-10-29 | 2019-04-02 | 太平湾发电厂 | Arrester resistance current on-line monitoring method based on hanning window phase difference method |
| CN110988475B (en) * | 2019-11-07 | 2021-01-01 | 武汉大学 | Non-contact transformer substation zinc oxide arrester bus voltage phase online monitoring method |
Citations (5)
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| EP0908735A3 (en) * | 1997-10-10 | 2001-09-12 | DaimlerChrysler Aerospace Aktiengesellschaft | Method for determining the frequency of a signal |
| CN102288804A (en) * | 2011-07-20 | 2011-12-21 | 南京世都科技有限公司 | Method for calculating resistive current of arrester based on orthogonal transformation |
| CN102435815A (en) * | 2011-10-21 | 2012-05-02 | 江苏技术师范学院 | Operating method of resistive current on-line monitoring system of metal oxide arrester (MOA) |
| CN104459280A (en) * | 2014-12-19 | 2015-03-25 | 南京信息工程大学 | Method for extracting resistance current of metal oxide arrester (MOA) |
| CN104459296A (en) * | 2013-11-27 | 2015-03-25 | 南京世都科技有限公司 | Resistive current measuring method and device based on forward and inverse FFT relative calibration |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0908735A3 (en) * | 1997-10-10 | 2001-09-12 | DaimlerChrysler Aerospace Aktiengesellschaft | Method for determining the frequency of a signal |
| CN102288804A (en) * | 2011-07-20 | 2011-12-21 | 南京世都科技有限公司 | Method for calculating resistive current of arrester based on orthogonal transformation |
| CN102435815A (en) * | 2011-10-21 | 2012-05-02 | 江苏技术师范学院 | Operating method of resistive current on-line monitoring system of metal oxide arrester (MOA) |
| CN104459296A (en) * | 2013-11-27 | 2015-03-25 | 南京世都科技有限公司 | Resistive current measuring method and device based on forward and inverse FFT relative calibration |
| CN104459280A (en) * | 2014-12-19 | 2015-03-25 | 南京信息工程大学 | Method for extracting resistance current of metal oxide arrester (MOA) |
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