CN110231548A - A kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum - Google Patents
A kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1209—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing using acoustic measurements
Abstract
The invention belongs to the insulation defect fault diagnosis technology field GIS more particularly to a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum, this method can help to identify different types of shelf depreciation insulation defect.Include: three kinds of GIS Exemplary insulative defects of design, acquires shelf depreciation ultrasonic signal；Partial discharge ultrasonic signal is filtered using FIR bandpass filter；Envelope extraction is carried out to filtered type local-discharge ultrasonic signal using Hilbert transformation；Power frequency correlation and phase pattern analysis are carried out to signal envelope, obtain the measurement feature of different defect types.The ultrasonic signal that the present invention is detected according to GIS partial discharge proposes the GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum.The present invention is based on the envelope spectrums of ultrasonic signal, obtain the measurement feature such as frequency spectrum, phase distribution of various typical defects, lay the foundation for the Classifcation of flaws of type local-discharge ultrasonic signal.
Description
Technical field
The invention belongs to GIS insulation defect fault diagnosis technology fields, more particularly to one kind to be based on ultrasonic signal envelope spectrum
GIS partial discharge feature extracting method, this method can help to identify different types of shelf depreciation insulation defect.
Background technique
Gas insulated metal enclosed swit chgear (Gas Insulated Switchgear, GIS) is one kind with SF6Gas is as insulation
The Cubicle Gas-Insulated Switchgear of medium.Compared with traditional open type substation, GIS is small with occupied area, transports
The remarkable advantages such as row high reliablity, high safety, maintenance cycle length.Therefore since the sixties in 20th century is practical, GIS exists
It is used widely in domestic and international electric system.
Due to the GIS popularity applied in power grid and its significance level, can its operating condition and entire power grid just
Normal trouble free service is closely bound up.Its same of situation of insulating can grasped by carrying out on-line monitoring fault identification to GIS partial discharge
When avoid stoppage in transit bring from negatively affecting, for guaranteeing that the safe and stable operation of entire electric system is of great significance.
Summary of the invention
The purpose of the present invention is in order to overcome the deficiencies of the prior art, provide a kind of GIS based on ultrasonic signal envelope spectrum
Local discharge characteristic extracting method.Its purpose is to the envelope spectrums based on ultrasonic signal, obtain the frequency of various typical defects
Spectrum, phase distribution etc. measure feature, lay the foundation for the Classifcation of flaws of type local-discharge ultrasonic signal.
To achieve the above object, the present invention adopts the following technical solutions to realize:
A kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum, includes the following steps:
Step 1: three kinds of GIS Exemplary insulative defects of design acquire shelf depreciation ultrasonic signal；
Step 2: partial discharge ultrasonic signal being filtered using FIR bandpass filter；
Step 3: envelope extraction being carried out to filtered type local-discharge ultrasonic signal using Hilbert transformation；
Step 4: power frequency correlation being carried out to signal envelope and phase pattern is analyzed, obtains the measurement of different defect types
Feature.
The FIR is that Finite Impulse Response has limit for length's unit impulse response filter；It is described
Hilbert is Hilbert transform, i.e., a kind of signal processing algorithm proposed by mathematician's Hilbert.
The step 1: three kinds of GIS Exemplary insulative defects of design acquire the specific method packet of shelf depreciation ultrasonic signal
It includes:
Firstly, the manufacturing process of three kinds of GIS Exemplary insulative defects are as follows:
(1) when making GIS high-pressure conductor metal needle point model, high-pressure conductor tip, two electricity are made with aluminum metal material
Interpolar is apart chosen between 15mm to 20mm, the corona discharge in Simulated GlS；
(2) when making suspension electrode model, a cylinder is made with epoxy resin, places piece of metal wherein, cylinder
Upper and lower surface apply respectively with high pressure and ground connection, then the metal in epoxy resin can approximation regard a suspension electrode, Simulated GlS as
In suspended discharge；
(3) when making free metal corpuscular model, a prill is placed between upper/lower electrode to simulate free gold
Belong to particulate electric discharge.
The step 2: being filtered partial discharge ultrasonic signal using FIR bandpass filter, is the power supply with 220V
Hyperbaric environment is obtained after auto-transformer T1 and step-up transformer T2, is connected to by current-limiting impedance Z and coupled capacitor
GIS tests cavity；Ultrasonic sensor is placed in the outside of GIS test cavity, for acquiring raw ultrasound letter when shelf depreciation
Number, which is transmitted to oscillograph after filter amplifier amplifies；Three insulation defect models are successively placed on GIS test
In cavity, and it is filled in insulation defect model the SF6 gas of 0.4MPa, pressurization is until generate stable discharge signal.
The step 2: include: using the specific method that FIR bandpass filter is filtered partial discharge ultrasonic signal
The linear phase shift property having is filtered using FIR, and the filtering of 500 rank FIR digital band passes is made to data, removes data
Higher hamonic wave interference and Hz noise, improve signal-to-noise ratio；The design of filter is realized using window function metht, comprising following
Step:
A. frequency response function required by filter is given:
If the group delay of linear-phase filter is τ, then the ideal frequency response of FIR filter are as follows:
In above formula (1): H is frequency response function, and subscript d represents Infinite Sequences, and e is natural constant, and j is plural
Imaginary part unit, w indicate frequency independent variable, and τ is group delay；
B. filter unit impulse response, i.e. fourier inverse transformation are asked:
In above formula (2): h is unit impulse response function, and subscript d represents Infinite Sequences, n be filter sequence from
Variable, H are frequency response functions, and e is natural constant, and j is the imaginary part unit of plural number, and w indicates frequency, and τ is group delay；
C. it is declined the requirement of alkali by transition band width and stopband, by the shape for selected window function of tabling look-up, and calculates filter order
It is secondary；
D. the unit impulse response of FIR filter is found out；
In above formula (3): h is unit impulse response function, and subscript d represents Infinite Sequences, and no subscript d representative has limit for length
Sequence, n are the sequence independents variable of filter, and ω (n) indicates that the window function of finite length, e are natural constants, and j is the void of plural number
Portion's unit, w indicate frequency, and τ is group delay；
E. the frequency response of filter, i.e. Fourier transform are asked；
In above formula (4): H is frequency response function, and e is natural constant, and j is the imaginary part unit of plural number, and w indicates frequency, under
Mark d represents Infinite Sequences, and no subscript d represents finite length sequence, and θ is frequency delay；
F. it checks whether to meet design requirement, such as be unsatisfactory for, then need to redesign；
Finally, the transmission function of FIR filter is write as:
In above formula (5): H is filter transfer function, and z indicates that discrete independent variable, Y are that filter exports discrete signal,
X is that filter inputs discrete signal, and b represents each term coefficient, and n represents order.
The FIR filter is exactly the process of each term coefficient in its determining transmission function, is believed with the SPTOOL of MATLAB
Number handling implement case visualizes filter design, designs linear phase fir bandpass filter with Hanning window function metht.
The step 3: the specific side of envelope extraction is carried out to filtered type local-discharge ultrasonic signal using Hilbert transformation
Method includes:
Firstly, original signal is converted into Hilbert form, envelope value A (t) then is calculated, if shelf depreciation ultrasound is believed
Number be x (t), Hilbert transform definition are as follows:
In above formula (6):It is signal x through the transformed function of Hilbert, t is time independent variable, and H indicates that Hilbert becomes
Filter is changed, x is original signal, and τ is the time change amount for making convolution algorithm；
The Hilbert transformation of signal x (t) can regard as signal by amplitude be 1 all-pass filter it is defeated
Out, for signal x (t) after the transformation, positive frequency component does -90 ° of phase shift, and negative frequency component does+90 ° of phase shift；
Hilbert filter is 90 ° of phase-shift networks of a wildcard-filter style, and impulse response is
With signal itself x (t) for real part, Hilbert transformationAn analytic signal is constructed for imaginary part:
In above formula (7)-(8): x is original signal, and subscripting a indicates analytic signal, and t is time independent variable, and j is plural number
Imaginary part unit,It is signal x through the transformed function of Hilbert, A is the amplitude of analytic signal, and e is nature Changshu, and Q is solution
Analyse the phase of signal；
The amplitude A (t) of analytic signal is exactly the envelope of actual signal x (t), and the phase Q (t) of analytic signal is exactly practical
The phase of signal x (t), the above process just complete the solution Envelope Analysis to signal, and the envelope extraction of signal is come out.
The step 4: power frequency correlation is carried out to signal envelope and phase pattern is analyzed, obtains different defect types
Measurement feature specific method include:
It first to extracted signal envelope further progress spectrum analysis, obtains: suspension electrode flaw indication 100Hz
Composition be apparently higher than 50Hz composition, it is periodical that stronger 100Hz is presented in the envelope spectrum of signal；Corona flaw indication 50Hz's
Composition is higher than 100Hz composition, and the envelope spectrum of signal shows the cyclophysis of 50Hz；The ultrasound that particle and shell collision generate
Signal and power frequency period non-correlation；
Phase pattern analysis further is carried out to envelope signal, obtain: the sound wave pulse of suspension electrode defect mainly occurs
Power frequency period one, three quadrant, have bimodal phase distribution form；Corona defect discharge signal each period only goes out
An existing minor peaks, ultrasonic signal have unimodal phase distribution form；Have in each phase interval of free metal particle defects
A considerable amount of distribution of pulses, without apparent phase correlation.
According to the diagnostic result of three kinds of GIS Exemplary insulative defect type, obtain carrying out different when ultrasound partial discharge diagnosis
The measurement feature of type flaw, learns, different defects have significant difference, energy based on the measurement feature of ultrasonic signal envelope spectrum
Enough Classifcation of flaws for being effectively used for Partial discharge signal.
The invention has the following advantages and beneficial effects:
The ultrasonic signal that the present invention is detected according to GIS partial discharge is proposed based on ultrasonic signal envelope spectrum
GIS partial discharge feature extracting method.3 kinds of GIS Exemplary insulative defects are designed first, and acquire shelf depreciation ultrasonic signal.Its
It is secondary that it is filtered using FIR bandpass filter, filtered type local-discharge ultrasonic is believed using Hilbert transformation later
Number carry out envelope extraction.Finally, carrying out power frequency correlation and phase pattern analysis to signal envelope, different defect types are obtained
Measurement feature.
Detailed description of the invention
Understand for the ease of those of ordinary skill in the art and implement the present invention, with reference to the accompanying drawing and specific embodiment party
The present invention is described in further detail for formula, and the following examples are intended to illustrate the invention, it is to be understood that protection of the invention
Range is not limited by the specific implementation.
Fig. 1 is measuring system test connection figure of the present invention；
Fig. 2 is the suspended discharge type signal under GIS insulation defect model of the present invention；
Fig. 3 is the corona discharge type signal under GIS insulation defect model of the present invention；
Fig. 4 is the free metal particulate electric discharge signal under GIS insulation defect model of the present invention；
Fig. 5 is FIR bandpass filter amplitude-versus-frequency curve of the present invention；
Fig. 6 is FIR bandpass filter phase-frequency characteristic curve of the present invention；
Fig. 7 is present invention actual measurement suspension electrode defect FIR filter effect figure and its FFT spectrum comparison diagram；
Fig. 8 is present invention actual measurement corona defect FIR filter effect figure and its FFT spectrum comparison diagram；
Fig. 9 is Hilbert converter frequency characteristic of the present invention；
Figure 10 is the filtered envelope signal of original signal under suspension electrode defect of the present invention；
Figure 11 is the filtered envelope signal of original signal under corona defect of the present invention；
Figure 12 is the filtered envelope signal of original signal under free metal particle defects of the present invention；
Figure 13 is the FFT spectrum figure of suspension electrode defect lower envelope signal of the present invention；
Figure 14 is the FFT spectrum figure of corona defect lower envelope signal of the present invention；
Figure 15 is the FFT spectrum figure of free metal particle defects lower envelope signal of the present invention；
Figure 16 is the phase distribution figure of suspension electrode defect lower envelope signal of the present invention；
Figure 17 is the phase distribution figure of corona defect lower envelope signal of the present invention；
Figure 18 is the phase distribution figure of free metal particle defects lower envelope signal of the present invention.
In figure: ultrasonic sensor 1, insulation defect model 2, GIS test cavity 3, coupled capacitor 4, current-limiting impedance Z, self coupling
Transformer T1, step-up transformer T2.
Specific embodiment
The present invention is a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum, including following steps
It is rapid:
Step 1: three kinds of GIS Exemplary insulative defects of design acquire shelf depreciation ultrasonic signal；
Step 2: partial discharge ultrasonic signal being filtered using FIR bandpass filter；
The FIR is that Finite Impulse Response has limit for length's unit impulse response filter.
Step 3: envelope extraction being carried out to filtered type local-discharge ultrasonic signal using Hilbert transformation；
The Hilbert is Hilbert transform, i.e., a kind of signal processing algorithm proposed by mathematician's Hilbert.
Step 4: power frequency correlation being carried out to signal envelope and phase pattern is analyzed, obtains the measurement of different defect types
Feature.
The step 1: three kinds of GIS Exemplary insulative defects of design acquire the specific method packet of shelf depreciation ultrasonic signal
It includes:
Firstly, the manufacturing process of three kinds of GIS Exemplary insulative defects are as follows:
(2) when making GIS high-pressure conductor metal needle point model, high-pressure conductor tip, two electricity are made with aluminum metal material
Interpolar is apart chosen between 15mm to 20mm, the corona discharge in Simulated GlS.
(2) when making suspension electrode model, a cylinder is made with epoxy resin, places piece of metal wherein, cylinder
Upper and lower surface apply respectively with high pressure and ground connection, then the metal in epoxy resin can approximation regard a suspension electrode, Simulated GlS as
In suspended discharge.
(3) when making free metal corpuscular model, a prill is placed between upper/lower electrode to simulate free gold
Belong to particulate electric discharge.
Measuring system test connection figure is as shown in Figure 1, pass through auto-transformer T1 and step-up transformer with the power supply of 220V
Hyperbaric environment is obtained after T2, and GIS is connected to by current-limiting impedance Z and coupled capacitor 4 and tests cavity 3.Ultrasonic sensor 1 is placed in
GIS tests the outside of cavity 3, for acquiring raw ultrasound signal when shelf depreciation.The signal is after filter amplifier amplifies
It is transmitted to oscillograph.When experiment, successively three insulation defect models 2 are placed in GIS test cavity 3, and in insulation defect
The SF6 gas of 0.4MPa is filled in model 2, pressurization is until generate stable discharge signal.
As shown in figs 2-4, Fig. 2 is GIS insulation defect of the present invention to the typical type local-discharge ultrasonic signal graph of three kinds of discharge defects
Suspended discharge type signal under model, Fig. 3 are the corona discharge type signal under GIS insulation defect model of the present invention, Fig. 4
It is the free metal particulate electric discharge signal under GIS insulation defect model of the present invention.
The step 2: include: using the specific method that FIR bandpass filter is filtered partial discharge ultrasonic signal
The linear phase shift property having is filtered using FIR, and the filtering of 500 rank FIR digital band passes is made to data, can be removed
The higher hamonic wave interference of data and Hz noise improve signal-to-noise ratio.The design that filter is realized using window function metht includes
The following steps:
A. frequency response function required by filter is given
If the group delay of linear-phase filter is τ, then the ideal frequency response of FIR filter are as follows:
In above formula (1): H is frequency response function, and subscript d represents Infinite Sequences, and e is natural constant, and j is the void of plural number
Portion's unit, w indicate frequency independent variable, and τ is group delay.
B. filter unit impulse response, i.e. fourier inverse transformation are asked:
In above formula (2): h is unit impulse response function, and subscript d represents Infinite Sequences, n be filter sequence from
Variable, H are frequency response functions, and e is natural constant, and j is the imaginary part unit of plural number, and w indicates frequency, and τ is group delay.
C. it is declined the requirement of alkali by transition band width and stopband, by the shape for selected window function of tabling look-up, and calculates filter order
It is secondary；
D. the unit impulse response of FIR filter is found out；
In above formula (3): h is unit impulse response function, and subscript d represents Infinite Sequences, and no subscript d representative has limit for length
Sequence, n are the sequence independents variable of filter, and ω (n) indicates that the window function of finite length, e are natural constants, and j is the void of plural number
Portion's unit, w indicate frequency, and τ is group delay.
E. the frequency response of filter, i.e. Fourier transform are asked；
In above formula (4): H is frequency response function, and e is natural constant, and j is the imaginary part unit of plural number, and w indicates frequency, under
Mark d represents Infinite Sequences, and no subscript d represents finite length sequence, and θ is frequency delay.
F. it checks whether to meet design requirement, such as be unsatisfactory for, then need to redesign.
Finally, the transmission function of FIR filter can be write as:
In above formula (5): H is filter transfer function, and z indicates that discrete independent variable, Y are that filter exports discrete signal,
X is that filter inputs discrete signal, and b represents each term coefficient, and n represents order.
As it can be seen that design FIR filter is exactly the process of each term coefficient in its determining transmission function, with MATLAB's
SPTOOL Matlab DSPToolBox visualizes filter design, designs linear phase fir bandpass filtering with Hanning window function metht
The frequency response curve of device, designed bandpass filter is as shown in Figure 5 and Figure 6, and Fig. 5 is FIR bandpass filter amplitude-frequency of the present invention
Characteristic curve, Fig. 6 are FIR bandpass filter phase-frequency characteristic curves of the present invention.
The measured data of suspension electrode electric discharge and two kinds of defect types of corona discharge is filtered, Fig. 7 and Fig. 8
The FIR filter effect figure and its FFT spectrum comparison diagram of two kinds of defects of actual measurement is set forth.
The step 3: the specific side of envelope extraction is carried out to filtered type local-discharge ultrasonic signal using Hilbert transformation
Method includes:
Firstly, original signal is converted into Hilbert form, then envelope value A (t) is calculated.If shelf depreciation ultrasound is believed
Number be x (t), Hilbert transform definition are as follows:
In above formula (6):It is signal x through the transformed function of Hilbert, t is time independent variable, and H indicates that Hilbert becomes
Filter is changed, x is original signal, and τ is the time change amount for making convolution algorithm.
The Hilbert transformation of signal x (t) can regard as signal by amplitude be 1 all-pass filter it is defeated
Out, for signal x (t) after the transformation, positive frequency component does -90 ° of phase shift, and negative frequency component does+90 ° of phase shift.
Hilbert filter is 90 ° of phase-shift networks of a wildcard-filter style, and impulse response isIts frequency characteristic is as shown in Figure 9.
With signal itself x (t) for real part, Hilbert transformationAn analytic signal is constructed for imaginary part:
In above formula (7)-(8): x is original signal, and subscripting a indicates analytic signal, and t is time independent variable, and j is plural number
Imaginary part unit,It is signal x through the transformed function of Hilbert, A is the amplitude of analytic signal, and e is nature Changshu, and Q is solution
Analyse the phase of signal.
The amplitude A (t) of analytic signal is exactly the envelope of actual signal x (t), and the phase Q (t) of analytic signal is exactly practical
The phase of signal x (t), the above process just complete the solution Envelope Analysis to signal, and the envelope extraction of signal is come out.No
With the envelope obtained after shelf depreciation ultrasonic signal filtering under defect as shown in Figure 10-Figure 12, Figure 10 is suspension electrode of the present invention
The filtered envelope signal of original signal under defect, Figure 11 are the filtered envelope signals of original signal under corona defect of the present invention, figure
12 be the filtered envelope signal of original signal under free metal particle defects of the present invention.
The step 4: power frequency correlation is carried out to signal envelope and phase pattern is analyzed, obtains different defect types
Measurement feature specific method include:
First to extracted signal envelope further progress spectrum analysis, the FFT frequency spectrum of different defect lower envelope signals
For figure as shown in Figure 13-Figure 15, Figure 13 is the FFT spectrum figure of suspension electrode defect lower envelope signal of the present invention, and Figure 14 is the present invention
The FFT spectrum figure of corona defect lower envelope signal, Figure 15 are the FFT frequencies of free metal particle defects lower envelope signal of the present invention
Spectrogram.
As can be seen that the composition of suspension electrode flaw indication 100Hz is apparently higher than 50Hz composition, the envelope spectrum of signal is in
Existing stronger 100Hz is periodical；The composition of corona flaw indication 50Hz is higher than 100Hz composition, and the envelope spectrum of signal shows
The cyclophysis of 50Hz；The ultrasonic signal and power frequency period non-correlation that particle and shell collision generate.
Phase pattern analysis further is carried out to envelope signal, as a result as exemplified in figs, Figure 16 is that the present invention is outstanding
The phase distribution figure of floating electrode defects lower envelope signal, Figure 17 is the phase distribution figure of corona defect lower envelope signal of the present invention,
Figure 18 is the phase distribution figure of free metal particle defects lower envelope signal of the present invention.
As can be seen that the sound wave pulse of suspension electrode defect mainly appear on power frequency period one, three quadrant, have
Bimodal phase distribution form；Only there are a minor peaks in corona defect discharge signal each period, and ultrasonic signal has unimodal
Phase distribution form；There are a considerable amount of distribution of pulses in each phase interval of free metal particle defects, without apparent
Phase correlation.
In summary the diagnostic result of three kinds of defect types, different type lacks when available progress ultrasound partial discharge diagnosis
Sunken measurement feature, as shown in table 1.
It, can by table 1 it can be found that different defects have significant difference based on the measurement feature of ultrasonic signal envelope spectrum
To be effectively used for the Classifcation of flaws of Partial discharge signal.
The measurement feature of 1 different type defect of table
| Signal characteristic quantity | Suspension electrode | Corona defect | Free metal particle |
| Signal level | It is high | It is low | It is high |
| Peak value/virtual value | It is high | It is low | It is high |
| Peak-to-peak value | It is high | It is low | It is high |
| Degree of skewness | It is small | It is small | Greatly |
| Kurtosis | Greatly | It is small | Greatly |
| Rise time | It is small | It is small | It is small |
| Fall time | It is small | Greatly | It is small |
| Pulse width at 50% peak value | It is small | Greatly | It is small |
| 50Hz frequency dependence | It is weak | By force | Nothing |
| 100Hz frequency dependence | By force | It is weak | Nothing |
| Phase correlation | It is bimodal | It is unimodal | Nothing |
Claims (9)
1. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum, it is characterized in that: including the following steps:
Step 1: three kinds of GIS Exemplary insulative defects of design acquire shelf depreciation ultrasonic signal；
Step 2: partial discharge ultrasonic signal being filtered using FIR bandpass filter；
Step 3: envelope extraction being carried out to filtered type local-discharge ultrasonic signal using Hilbert transformation；
Step 4: power frequency correlation being carried out to signal envelope and phase pattern is analyzed, obtains the measurement feature of different defect types.
2. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum according to claim 1, special
Sign is: the FIR is that Finite Impulse Response has limit for length's unit impulse response filter；The Hilbert is
Hilbert transform, i.e., a kind of signal processing algorithm proposed by mathematician's Hilbert.
3. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum according to claim 1, special
Sign is: the step 1: the specific method of three kinds of GIS Exemplary insulative defects of design, acquisition shelf depreciation ultrasonic signal includes:
Firstly, the manufacturing process of three kinds of GIS Exemplary insulative defects are as follows:
(1) when making GIS high-pressure conductor metal needle point model, high-pressure conductor tip is made with aluminum metal material, between two electrodes
It is apart chosen between 15mm to 20mm, the corona discharge in Simulated GlS；
(2) when making suspension electrode model, a cylinder is made with epoxy resin, places piece of metal wherein, cylinder up and down
Surface applies respectively with high pressure and ground connection, then the metal in epoxy resin can approximation regard a suspension electrode as, it is outstanding in Simulated GlS
Floating electric discharge；
(3) when making free metal corpuscular model, it is micro- to simulate free metal that a prill is placed between upper/lower electrode
Grain electric discharge.
4. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum according to claim 1, special
Sign is: the step 2: being filtered using FIR bandpass filter to partial discharge ultrasonic signal, is passed through with the power supply of 220V
Hyperbaric environment is obtained after auto-transformer T1 and step-up transformer T2, GIS test is connected to by current-limiting impedance Z and coupled capacitor
Cavity；Ultrasonic sensor is placed in the outside of GIS test cavity, for acquiring raw ultrasound signal when shelf depreciation, the signal
Oscillograph is transmitted to after filter amplifier amplifies；Successively three insulation defect models are placed in GIS test cavity, and
The SF6 gas of 0.4MPa is filled in insulation defect model, pressurization is until generate stable discharge signal.
5. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum according to claim 1, special
Sign is: the step 2: including: using the specific method that FIR bandpass filter is filtered partial discharge ultrasonic signal
The linear phase shift property having is filtered using FIR, and the filtering of 500 rank FIR digital band passes is made to data, removes the high order of data
Harmonic wave interference and Hz noise improve signal-to-noise ratio；The design of filter is realized using window function metht comprising the steps of:
A. frequency response function required by filter is given:
If the group delay of linear-phase filter is τ, then the ideal frequency response of FIR filter are as follows:
In above formula (1): H is frequency response function, and subscript d represents Infinite Sequences, and e is natural constant, and j is the imaginary part list of plural number
Position, w indicate frequency independent variable, and τ is group delay；
B. filter unit impulse response, i.e. fourier inverse transformation are asked:
In above formula (2): h is unit impulse response function, and subscript d represents Infinite Sequences, and n is the sequence independent variable of filter, H
It is frequency response function, e is natural constant, and j is the imaginary part unit of plural number, and w indicates frequency, and τ is group delay；
C. it is declined the requirement of alkali by transition band width and stopband, by the shape for selected window function of tabling look-up, and calculates filter order；
D. the unit impulse response of FIR filter is found out；
In above formula (3): h is unit impulse response function, and subscript d represents Infinite Sequences, and no subscript d represents finite length sequence, n
It is the sequence independent variable of filter, ω (n) indicates that the window function of finite length, e are natural constants, and j is the imaginary part unit of plural number,
W indicates frequency, and τ is group delay；
E. the frequency response of filter, i.e. Fourier transform are asked；
In above formula (4): H is frequency response function, and e is natural constant, and j is the imaginary part unit of plural number, and w indicates frequency, subscript d generation
Table Infinite Sequences, no subscript d represent finite length sequence, and θ is frequency delay；
F. it checks whether to meet design requirement, such as be unsatisfactory for, then need to redesign；
Finally, the transmission function of FIR filter is write as:
In above formula (5): H is filter transfer function, and z indicates that discrete independent variable, Y are that filter exports discrete signal, and X is filter
Wave device inputs discrete signal, and b represents each term coefficient, and n represents order.
6. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum according to claim 5, special
Sign is: the FIR filter is exactly the process of each term coefficient in its determining transmission function, at the SPTOOL signal of MATLAB
It manages tool box and visualizes filter design, design linear phase fir bandpass filter with Hanning window function metht.
7. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum according to claim 1, special
Sign is: the step 3: carrying out the specific method packet of envelope extraction to filtered type local-discharge ultrasonic signal using Hilbert transformation
It includes:
Firstly, original signal is converted into Hilbert form, envelope value A (t) then is calculated, if shelf depreciation ultrasonic signal is x
(t), Hilbert transform definition are as follows:
In above formula (6):It is signal x through the transformed function of Hilbert, t is time independent variable, and H indicates Hilbert transformation filter
Wave device, x are original signals, and τ is the time change amount for making convolution algorithm；
The Hilbert transformation of signal x (t) can regard the output for the all-pass filter that signal is 1 by an amplitude, signal as
For x (t) after the transformation, positive frequency component does -90 ° of phase shift, and negative frequency component does+90 ° of phase shift；Hilbert filter
It is 90 ° of phase-shift networks of a wildcard-filter style, impulse response is
With signal itself x (t) for real part, Hilbert transformationAn analytic signal is constructed for imaginary part:
In above formula (7)-(8): x is original signal, and subscripting a indicates analytic signal, and t is time independent variable, and j is the imaginary part of plural number
Unit,It is signal x through the transformed function of Hilbert, A is the amplitude of analytic signal, and e is nature Changshu, and Q is analytic signal
Phase；
The amplitude A (t) of analytic signal is exactly the envelope of actual signal x (t), and the phase Q (t) of analytic signal is exactly actual signal x
(t) phase, the above process just complete the solution Envelope Analysis to signal, and the envelope extraction of signal is come out.
8. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum according to claim 1, special
Sign is: the step 4: carrying out power frequency correlation to signal envelope and phase pattern is analyzed, obtain the measurement of different defect types
The specific method of feature includes:
It first to extracted signal envelope further progress spectrum analysis, obtains: the composition of suspension electrode flaw indication 100Hz
It is apparently higher than 50Hz composition, it is periodical that stronger 100Hz is presented in the envelope spectrum of signal；The composition of corona flaw indication 50Hz is higher than
The envelope spectrum of 100Hz composition, signal shows the cyclophysis of 50Hz；The ultrasonic signal and power frequency that particle and shell collision generate
Period non-correlation；
Phase pattern analysis further is carried out to envelope signal, obtain: the sound wave pulse of suspension electrode defect mainly appears on
Power frequency period one, three quadrant, have bimodal phase distribution form；Corona defect discharge signal each period only occurs once
Peak value, ultrasonic signal have unimodal phase distribution form；Have in each phase interval of free metal particle defects and quite counts
The distribution of pulses of amount, without apparent phase correlation.
9. a kind of GIS partial discharge feature extracting method based on ultrasonic signal envelope spectrum according to claim 1, special
Sign is: according to the diagnostic result such as table 1 of three kinds of GIS Exemplary insulative defect type, when obtaining carrying out ultrasound partial discharge diagnosis not
The measurement feature of same type defect, learns, different defects have significant difference, energy based on the measurement feature of ultrasonic signal envelope spectrum
Enough Classifcation of flaws for being effectively used for Partial discharge signal.
The measurement feature of 1 different type defect of table
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