CN102565646A - Lightning-wave surge-voltage type test device for dry sleeve and frequency band analysis method thereof - Google Patents

Lightning-wave surge-voltage type test device for dry sleeve and frequency band analysis method thereof Download PDF

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Publication number
CN102565646A
CN102565646A CN2012100149248A CN201210014924A CN102565646A CN 102565646 A CN102565646 A CN 102565646A CN 2012100149248 A CN2012100149248 A CN 2012100149248A CN 201210014924 A CN201210014924 A CN 201210014924A CN 102565646 A CN102565646 A CN 102565646A
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China
Prior art keywords
sleeve pipe
sleeve
sequence
lightning
capacitance
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CN2012100149248A
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Chinese (zh)
Inventor
王红斌
喇元
柯春俊
朱文俊
吴锴
何宝声
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广东电网公司电力科学研究院
西安交通大学
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Priority to CN2012100149248A priority Critical patent/CN102565646A/en
Publication of CN102565646A publication Critical patent/CN102565646A/en

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Abstract

The invention provides a lightning-wave surge-voltage type test device for a dry sleeve and a frequency band analysis method thereof, belonging to an insulation state monitoring technology of large-sized electrical equipment and mainly being used for monitoring whether breakdown of a dry sleeve occurs in a lightning-wave type test and monitoring the number of breakdown layers. The test device and the analysis method aim at the following two problems in the current dry sleeve lightning-wave surge-voltage type test: (1) when more sleeve layers and extremely few breakdown layers exist, the change of the sleeve capacitance values before and after the test is not obvious; and (2) in the process of the lightning-wave type test, response wave forms do not have obvious change regardless of whether the breakdown of the dry sleeve occurs. In order to solve the problems, an extra capacitor is connected with a main insulating core of a sleeve in series to ground and the voltages across two ends of the extra capacitor in the test are subjected to time-frequency analysis, so that the time point when the breakdown occurs and the number of the breakdown layers can be estimated.

Description

Dry sleeve lightning wave impulse voltage pattern test unit and frequency range analysis method thereof

Technical field

The invention belongs to large scale electrical power unit insulation state monitoring technology, relate to signal processing technology, particularly dry sleeve lightning wave impulse voltage pattern test unit and frequency range analysis method thereof.

Background technology

Insulating material all can only keep its insulation characterisitic once in certain electric field intensity, and when electric field intensity surpassed certain limit, insulating material just can lose insulation characterisitic moment, and entire equipment is destroyed.Therefore, dielectric strength is the most basic insulation characterisitic parameter.No matter in the production of electric product, still in use, all to often do the type approval test of dielectric strength.

Various high-voltage electrical equipments are in operation, and will suffer atmospheric over-voltage unavoidably.In order to check dry sleeve to bear this superpotential ability, need carry out the dielectric test [1] of surge voltage to it.In the dielectric test under the surge voltage, the surge voltage waveform of employing is the maximum surge voltage waveform of probability of occurrence in the simulation actual motion, and this is the various reference waveforms of stipulating out according to a large amount of results that survey statistics.According to GB/T16927.1-1997 " the high-voltage test part: ordinary test requires " regulation; General wave head time T 1 is 1.2 ± 30% μ s; Wave rear time T 2 is 50 ± 2% μ s, the shock wave peak value is no more than ± and 3%, the overbump oscillation amplitude that produces on the peak value is less than 5% of peak value.In general, can use formula (1) to represent that lightning wave is in t voltage U constantly:

U = A ( e - t t 1 - e - t t 2 ) - - - ( 1 )

Wherein: t 1=T 2/ ln 2, t 2=T 1/ 3.25, T1, T2 are respectively wave head time and wave rear time, and A is the shock wave amplitude.

Usually, dry sleeve can be regarded the series connection of a plurality of resistance capacitance parallel-connection structures as, shown in accompanying drawing 1.In the real work, the engineering staff is through the relevant voltage waveform of observation sleeve pipe under surge voltage on the voltage divider that is connected in parallel on sleeve pipe insulation core both sides, and the variation of measurement sleeve pipe capacitance before and after test is to confirm the puncture number of plies.But in fact, this method has two defectives: 1) the sleeve pipe number of plies is more and puncture the number of plies when few, before and after the test variation of capacitance of bushing value all very not obvious, make that the engineering staff is difficult to discover; 2) in lightning wave type approval test process, no matter whether whether sleeve pipe punctures its response wave shape is not had significant change, and promptly this method is not directly perceived.

Summary of the invention

Defective or deficiency to above-mentioned prior art exists the objective of the invention is to, and a kind of simple and effective method really is provided, and confirm whether punch-through takes place and puncture the number of plies at lightning wave type approval test middle sleeve.

For realizing above-mentioned purpose, the present invention adopts following technical scheme:

Dry sleeve lightning wave impulse voltage pattern test unit; Comprise the sleeve pipe main capacitance fuse and the extra capacitor that stand lightning wave type approval test and series connection each other as a whole; The two ends of said extra capacitor are connected with oscillograph; Data collecting card is gathered oscillographic signal and is transferred to computing machine, adopts Fourier analysis judgement in short-term to puncture the time of origin and the sleeve pipe puncture number of plies.

3 times of the capacitance that the said capacitance that adds electric capacity is sleeve pipe insulation core main capacitance at least;

Said data collecting card is the multi-channel digital capture card of picking rate more than 1GS/s.

The frequency range analysis method of dry sleeve lightning wave impulse voltage type approval test at first utilizes data collecting card to oscillographic waveform u 2(t) sample, and with sampled result u 2(n) be transferred to computing machine and preserving, computing machine is to sampled result u then 2(n) use a plurality of rectangular window function g i(n) carry out intercepting and handle, obtain a series of sequences Then, to sequence Carry out carrying out the normalization processing after the FFT, obtain sequence The numerical frequency amplitude response Through with the comparison of consecutive point amplitude response just can obtain sleeve pipe at a time the section whether puncture.

As the preferred embodiments of the present invention, to sampled result u 2(n) use a plurality of rectangular window function g i(n) carry out intercepting and handle after, carry out intercepting once more and handle, promptly remove In null value, keep nonzero value;

As the preferred embodiments of the present invention, the length of the secondary intercepting sequence that obtains is N i=n I+1-n i+ 1;

As the preferred embodiments of the present invention, said Wherein, [n i, n I+1] be window g i(n) block the interval;

As the preferred embodiments of the present invention, said u ~ i ( n ) = u 2 ( n ) * g i ( n ) .

Compared with prior art; Dry sleeve lightning wave impulse voltage pattern test unit of the present invention and frequency range analysis method thereof have the following advantages at least: the present invention utilizes the extra capacitor ground connection of connecting with sleeve pipe main capacitance fuse; Stand the lightning wave type approval test as a whole, and utilize in short-term Fourier analysis to puncture the number of plies and estimate puncturing time of origin and sleeve pipe exactly, so; Can not receive the interference of factors such as stray capacitance, judged result is comparatively accurate.

Description of drawings

Fig. 1 is a dry sleeve capacitance-resistance parallel-series structural representation in the background technology;

Fig. 2 is the lightning wave type approval test circuit diagram that the present invention proposes;

Fig. 3 is voltage u under Fig. 2 hookup 2(t) variation synoptic diagram comprises under the normal condition and punctures u when taking place 2(t) waveform;

Fig. 4 is that the present invention is to u 2(t) sampled result is carried out the process flow diagram of Fourier analysis in short-term;

Fig. 5 is u 2Frequency domain distortion synoptic diagram a) is under the normal condition wherein Amplitude response is when b) puncturing generation for wavefront Amplitude response is to puncture when taking place behind the ripple c) Amplitude response (for ecbatic more clearly, only provide and close on the distortional point place);

Fig. 6 is the frequency domain amplitude response of rectangular window of the present invention;

Fig. 7 is a test findings of the present invention; Wherein, Concern between the distorted position in the ratio e of breakdown layer capacitance value of sleeve pipe and sleeve pipe insulation core total capacitance value and frequency domain when a) puncturing generation, concern between the ratio e of breakdown layer capacitance value of sleeve pipe and sleeve pipe insulation core total capacitance value and the distortion degree E when b) puncturing generation for wavefront for wavefront; C), d) be that E concerns between ratio e and the distortion degree of the breakdown layer capacitance value of sleeve pipe and sleeve pipe insulation core total capacitance value when puncturing generation behind the ripple for concerning between the distorted position in the ratio e that punctures the breakdown layer capacitance value of sleeve pipe and sleeve pipe insulation core total capacitance value when taking place behind the ripple and frequency domain.

Embodiment

The present invention proposes to utilize the extra capacitor ground connection of connecting with sleeve pipe main capacitance fuse, stands the lightning wave type approval test as a whole.The capacitance of extra capacitor is much larger than the capacitance of sleeve pipe main capacitance fuse; In process of the test, bear most voltages like this by capacitance of bushing; Assurance adds electric capacity can be not breakdown in process of the test; In general, adding capacitor C 2 capacitances should be more than 3 times of sleeve pipe insulation core main capacitance C1 value at least.Using oscillograph observation to add capacitor C 2 voltage u 2(t) it is carried out uniform sampling waveform the time, and sampled signal is transferred to terminal carry out Fourier analysis in short-term, system architecture is shown in accompanying drawing 2.

How will combine Fig. 2 to Fig. 7 specifically to introduce this method below uses oscillograph to observe u 2(t) the puncture time of origin and the sleeve pipe puncture number of plies are estimated in waveform and analysis:

1) this method needs the oscillograph actual sample rate to be at least 50Mhz, and bandwidth is at least 200Mhz, and adjustment oscillograph triggering mode triggers for the single rising edge.Choose suitable channel oscilloscope and measure u through the voltage divider shown in the accompanying drawing 2 2(t) waveform.Evidence, when puncturing generation, the sudden change shown in accompanying drawing 4 takes place with display waveform in oscillograph;

2) the Usage data collection card is to u 2(t) in 0-1ms, sample, and with sampled result u 2(n) transfer in the computing machine and preservation, this method recommends to use the multi-channel digital capture card of picking rate more than 1GS/s;

3) to u 2(n) use a plurality of rectangular window function g i(n) carry out truncation, obtain a series of sequences Wherein:

[n i, n I+1] be window g i(n) block the interval;

u ~ i ( n ) = u 2 ( n ) * g i ( n ) , Then

Wherein, 3 points below the selection of window function must be satisfied: each g i(n) blocking burst length between can be different but block interval zero lap; Each g i(n) blocking interval position (for example: g distributes by number order 1(n) block interval be [1,1000], g 2(n) block interval be [1001,2000]); All g i(n) block burst length sum and sequence u 2(n) length is consistent.

The number of windows and each the window g that need i(n) block interval concrete length and choose by actual conditions, in general: sampled point is many more, and the window that needs is many more; g i(n) blocking interval minimum length must not be less than 1000, otherwise the error of follow-up work is bigger.

4) in order to practice thrift the calculator memory space and to improve the conversion speed in the follow-up work, need be to blocking sequence Carry out truncation once more: remove In null value, only keep nonzero value, obtain secondary and block sequence Its length is N i=n I+1-n i+ 1, promptly satisfy:

u ~ · i ( n ) = u ~ i ( n + n i - 1 ) ;

Wherein: n iWith n I+1Referring to step I i) middle rectangular window g i(n) definition;

5) to the sequence after the secondary intercepting Carry out carrying out the normalization processing behind the fast Fourier transform (FFT), obtain The numerical frequency amplitude response (owing to carried out the normalization processing, Maximal value is no more than 1), wherein Be secondary intercepting sequence At the discrete digital Frequency point (k=1,2, the spectrum value of 3...N) locating can be known secondary intercepting sequence by the Nyquist sampling theorem The discrete digital frequencies omega kCorresponding to the period Interior continuous voltage signal u 2(t) analog frequency value does (k=1,2,3...N), f wherein sBe step I) in SF;

6) under the normal condition, secondary blocks sequence Amplitude response With frequencies omega kMonotone decreasing; But work as sleeve pipe in the period When interior generation punctured, this period, pairing secondary blocked sequence The frequency amplitude response Can produce the distortion shown in accompanying drawing 5, distortion place spectral magnitude is all bigger than adjacent spectra amplitude.

Use the consecutive point relative method to judge that each amplitude response that is obtained by step 5) does not distort, can know whether whether sleeve pipe puncture in the period ;

7) definition u (n) for to the standard lightning wave in 0-1ms set by step 1) in the sequence that obtains after sampling of sampling rate, and is for to u (n) set by step 3) sequence of stages once more that obtains after handling with step 4). ? for FFT and normalized to obtain the corresponding amplitude response?

When distortion takes place at the frequencies omega place in definite amplitude response , definition distortion degree

E = | U ~ i ′ ( ω ) - U ~ i ( ω ) | U ~ i ′ ( ω ) ;

The breakdown layer capacitance value of definition sleeve pipe is e with the ratio of sleeve pipe insulation core total capacitance value, can be got between E value size and the e by a large amount of test findings statistics to concern roughly shown in accompanying drawing 6;

Known when the sleeve structure design, when promptly each layer capacitance of sleeve pipe and insulation core total capacitance are known, just can estimate that through the E value sleeve pipe punctures the number of plies in type approval test.

Can learn by step 6) and step 7) whether sleeve pipe punctures, puncture the roughly estimation that belongs to the period constantly and puncture the number of plies.

In fact, step 3), 4), 5) in work be Fourier analysis in short-term.Different with the Fourier analysis on the common meaning, Fourier analysis is in short-term only carried out spectrum analysis to the content of signal in a certain period, can be expressed as the Fourier analysis in short-term of continuous analog signal:

F ( ω ) = ∫ - ∞ + ∞ f ( t ) g ( t - τ ) e - jωt dt

Wherein, g (t) is window function, is removing the t=u part, and g (t) amplitude decays rapidly, is playing the effect of intercept signal f (t) in the t=u nearby content in the Fourier analysis in short-term.According to the uncertainty principle of Heisenburg, signal is carried out after the Fourier transform signal time domain width cs tAnd frequency domain width cs ωBetween satisfy:

σ tω=k≥0.5

That is, after signal time domain width was by brachymemma, its frequency domain width can extend, and this for the research sleeve pipe u in this instantaneous process takes place to puncture 2(t) variation of frequency spectrum is very favourable.

Select the reason of rectangular window to mainly contain 2 points: 1) the rectangular window pattern is comparatively simple, uses rectangular window to carry out that Fourier analysis is comparatively convenient in short-term; 2) the Gibbs effect brought of rectangular window can be ignored herein; In general; Because the response of the frequency domain amplitude of rectangular window is the sinc function; Shown in accompanying drawing 6; So the use rectangular window carries out the distortion that the FFT conversion might cause discrete signal cutoff frequency place after cutting the discrete signal that obtains of sampling again; But it is high by the lightning wave cutoff frequency; Puncture is far away apart from cutoff frequency to the range of influence of ; And amplitude is very little near cutoff frequency; The distortion that the Gibbs effect is brought can be ignored basically; So can affirm distortion be caused fully by puncturing, with to use rectangular window to block sampled signal irrelevant.

Generally speaking, to puncture the number of plies many more when wavefront, and the distortional point frequency amplitude is big more, and the distortion degree is also big more; The rule that punctures behind the ripple is then just opposite.This conclusion is seen and can be helped the engineering staff to make corresponding judgement according to analysis result.

The above is merely one embodiment of the present invention; It or not whole or unique embodiment; The conversion of any equivalence that those of ordinary skills take technical scheme of the present invention through reading instructions of the present invention is claim of the present invention and contains.

Claims (10)

1. dry sleeve lightning wave impulse voltage pattern test unit; It is characterized in that: comprise the sleeve pipe main capacitance fuse and the extra capacitor that stand lightning wave type approval test and series connection each other as a whole; The two ends of said extra capacitor are connected with oscillograph; Data collecting card is gathered oscillographic signal and is transferred to computing machine, adopts Fourier analysis judgement in short-term to puncture the time of origin and the sleeve pipe puncture number of plies.
2. dry sleeve lightning wave impulse voltage pattern test unit according to claim 1 is characterized in that: 3 times of the capacitance that the said capacitance that adds electric capacity is sleeve pipe insulation core main capacitance at least.
3. dry sleeve lightning wave impulse voltage pattern test unit according to claim 1 is characterized in that: said data collecting card is the multi-channel digital capture card of picking rate more than 1GS/s.
4. based on the frequency range analysis method of the described dry sleeve lightning wave impulse of claim 1 voltage pattern test unit, it is characterized in that: at first utilize data collecting card oscillographic waveform u 2(t) sample, and with sampled result u 2(n) be transferred to computing machine and preserving, computing machine is to sampled result u then 2(n) use a plurality of rectangular window function g i(n) carry out intercepting and handle, obtain a series of sequences Then, to sequence Carry out carrying out the normalization processing after the FFT, obtain sequence The numerical frequency amplitude response Through with the comparison of consecutive point amplitude response just can obtain sleeve pipe at a time the section whether puncture.
5. analytical approach as claimed in claim 4 is characterized in that: to sampled result u 2(n) use a plurality of rectangular window function g i(n) carry out intercepting and handle after, carry out intercepting once more and handle, promptly remove In null value, keep nonzero value.
6. analytical approach as claimed in claim 4 is characterized in that: the length of the secondary intercepting sequence that obtains is N i=n I+1-n i+ 1.
7. like claim 4 or 5 described analytical approachs, it is characterized in that: said Wherein, [n i, n I+1] be window g i(n) block the interval.
8. analytical approach as claimed in claim 7 is characterized in that: said
9. based on the frequency range analysis method of the described dry sleeve lightning wave impulse of claim 1 voltage pattern test unit, it is characterized in that: may further comprise the steps:
(1) the Usage data collection card is to oscillographic waveform u 2(t) in 0-1ms, sample, and with sampled result u 2(n) transfer in the computing machine and preservation;
(2) to sampled result u 2(n) use a plurality of rectangular window function g i(n) carry out truncation, obtain a series of sequences
(3) to the sequence after the intercepting Carry out carrying out the normalization processing after the FFT, obtain The numerical frequency amplitude response Wherein, Be the intercepting sequence At the discrete digital Frequency point (k=1,2, the spectrum value of 3...N) locating, intercepting sequence The discrete digital frequencies omega kCorresponding to the period Interior continuous voltage signal u 2(t) analog frequency value does (k=1,2,3...N), f wherein sBe the SF in the step 1);
(4) under the normal condition, block sequence Amplitude response With frequencies omega kMonotone decreasing; When sleeve pipe in the period When interior generation punctures, the pairing sequence of blocking of this period The frequency amplitude response Can produce distortion, distortion place spectral magnitude is all bigger than adjacent spectra amplitude, uses the consecutive point relative method can judge that whether sleeve pipe is in the period In whether puncture.
10. analytical approach as claimed in claim 9; It is characterized in that: set: u (n) for to the standard lightning wave in 0-1ms set by step 1) in the sequence that obtains after sampling of sampling rate, is to u (n) set by step
3) sequence of stages once more that obtains after the processing; carried out obtain corresponding then distortion degree of amplitude response after FFT and the normalization be: sets: the capacitance of the breakdown layer of sleeve pipe is e with the ratio of sleeve pipe insulation core total capacitance value; Be the relation between the e then, can estimate that sleeve pipe punctures the number of plies in type approval test through the capacitance of the breakdown layer of contrast distortion degree E and sleeve pipe and the ratio of sleeve pipe insulation core total capacitance value.
CN2012100149248A 2012-01-16 2012-01-16 Lightning-wave surge-voltage type test device for dry sleeve and frequency band analysis method thereof CN102565646A (en)

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