CN101702000A - Phased ultrasound locating method and system of partial discharge of transformer - Google Patents

Abstract

The invention relates to a phased ultrasound locating method of the partial discharge of a transformer, which is used for monitoring and locating partial discharge faults. Phased array ultrasound sensors arranged at two different positions of the transformer are adopted to receive ultrasound broadband signals sent out by a partial discharge source, and an array model is formed; then a broadband focus algorithm in a broad-ban array signal processing algorithm is applied to convert broadband signals received by the two phased array ultrasound sensors into narrow-band signals, then a narrow-band direction finding algorithm is applied to respectively carry out direction of arrival (DOA) estimation on the two narrow-band signals, and finally a cross locating algorithm is applied to determine the concrete position of the partial discharge. Meanwhile, the invention also discloses a locating system. The invention can carry out on-line accurate locating on the partial discharge in the transformer; moreover, the used locating system has simple structure, and the method is simple and easy to apply.

Description

The phased ultrasound locating method of partial discharge of transformer and system

Technical field

The present invention relates to a kind of pick-up unit that is used to monitor the Partial Discharge in Power Transformer position, belong to the detection technique field.

Background technology

Along with development of productivity, more and more higher to the requirement of Operation of Electric Systems reliability, and power transformer is the hinge equipment in the electric system, its operational reliability is directly connected to the safety and stablization of electric system.To the statistical results show of physical fault, insulation fault is the main cause that influences the normal operation of transformer, and shelf depreciation is to cause the major reason of insulation fault.

Current, the state maintenance of development power equipment has become a kind of inexorable trend, and not only there is important booster action shelf depreciation location to the assessment of the extent of injury of shelf depreciation accurately, and can provide the guidance of science for the repair based on condition of component of transformer, so that the maintainer carries out maintenance of equipment with a definite target in view, fix a breakdown rapidly, improve the maintenance level, also the design of improvement transformer device structure, raising manufacturing technology level are had directive significance simultaneously.

Since the eighties in 20th century, detected existing a large amount of fundamental research and application and development work around partial discharge of transformer.At present, existing transformer partial discharge positioning method mainly contains three kinds of electrical Location method, superfrequency localization method and ultrasonic locating methods.

The electrical Location method is the method for carrying out analyzing and positioning according to partial discharge pulse along the Transformer Winding propagation law.The position that electric method is determined is electric position rather than the geometric position that shelf depreciation takes place, although at present the Transformer Winding characteristic has been carried out big quantity research, but, but seldom adopt electric method in practice, main cause is: at first, electric method execute-in-place complexity, its scope of application is subjected to bigger restriction; The second, bigger to the difficulty of the accurate modeling of Transformer Winding, it is loaded down with trivial details to work, and versatility is relatively poor; The 3rd, because the complicacy of transformer winding structure and the uncertainty of shelf depreciation occurrence positions, the pulse propagation rule of winding overhang is not strong, and accurate positioning is not high, and, being subjected to on-the-spot intense electromagnetic disturbing effect, electric method is difficult to effectively realize online application.

The ultrahigh frequency mensuration is measured the electromagnetic radiation of discharge generation, and its frequency band is between number MHz to 10MHz.It is strong and can reflect advantage such as the true waveform of discharge pulse that it has inhibition ability highly sensitive, that disturb to external world.For power transformer, shelf depreciation occurs in the interior oil-barrier insulation of transformer, because catadioptric and decay can take place repeatedly during electromagnetic wave propagation the complicacy of insulation system; Simultaneously, the transformer tank wall also can bring adverse effect to electromagnetic wave propagation, and this has just increased the difficulty that uhf electromagnetic wave detects, and therefore, transformer ultrahigh frequency office puts detection technique and still is in the starting stage.

The ultrasonic locating method is to determine the direction of the ultrasonic propagation that produces according to shelf depreciation and time that office puts the locus in source.Ultrasonic locating method principle is simple, and anti-electromagnetic interference capability is strong, and cost is low, can directly realize geometry location.The subject matter of this method existence has sonac sensitivity very low at present, can't measure signal at the scene effectively; Secondly the anti-electromagnetic interference capability of sensor is relatively poor, and ultrasonic signal is often because of the route of transmission, frequency, factor affecting distortions such as speed, and the conventional ultrasonic wave localization method also is confined to time-domain analysis, and precision is not high, and this also is to reach the problem that presses for solution in the practice theoretically.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art, a kind of phased ultrasound locating method that can fast, accurately determine the Partial Discharge in Power Transformer position is provided, the present invention gives positioning system simultaneously.

Problem of the present invention realizes with following technical proposals:

A kind of phased ultrasound locating method of partial discharge of transformer, the ultrasonic broadband signal that its employing places the phased array supersonic sensor office of acceptance source of putting of two diverse locations on the transformer to send, and formation Array Model, the broadband focusing algorithm of using then in the wideband Array Signal Processing algorithm converts the broadband signal that two phased array supersonic sensors are received to narrow band signal, use arrowband direction finding algorithm again two narrow band signals are carried out the direction of arrival estimation respectively, use the particular location that the cross bearing algorithm is determined shelf depreciation at last.

The phased ultrasound locating method of above-mentioned partial discharge of transformer, concrete operations are:

A, the ultrasonic broadband signal that adopts two phased array supersonic sensor office of acceptance sources of putting of being close to the transformer diverse location to send;

B, employing TCT broadband focusing algorithm are with the direction matrix A under the different frequency _β(f _j) transform to optimum reference frequency f ₀On:

Suppose that the broadband signal model is as follows: X (f _j)=A _β(f _j) S (f _j)+N (f _j) j=1,2 ..., J

S (f in the formula _j) be the data vector of signal, N (f _j) be that the j section receives data noise spatial data matrix,

Signal after then handling through focussing matrix is: T _β(f _j) X (f _j)=A _β(f ₀) S (f ₀)+N (f _j) j=1,2 ..., J

Wherein,

Be focussing matrix,

With

Be respectively span{P (f ₀) and span{P (f _j) orthogonal basis, P (f _j)=A _β(f _j) R _s(f _j) A _β ^H(f _j);

The source coordinate system is put in c, foundation office, establishes the phased array supersonic sensors A ₁, A ₂The plane, place is the XOY face, A ₁, A ₂Line is an X-axis, with A ₁For initial point is set up rectangular coordinate system, then office's coordinate of putting source S for (x, y, z);

D, adopt the MUSIC algorithm respectively two narrow band signals to be carried out direction of arrival to estimate, obtain the office that two phased array supersonic sensors record and put the position angle and the angle of pitch in source;

The position angle in source and the position of the angle of pitch and each phased array supersonic sensor are put in e, the office that records according to each phased array supersonic sensor, calculate out volume coordinate position of putting the source and are:

Wherein, θ ₁, θ ₂Be the position angle, θ ₁For source S point is put at XOY face subpoint S ' and A in office ₁Line A ₁The forward angle that S ' and X-axis form; θ ₂For source S point is put at XOY face subpoint S ' and A in office ₂Line A ₂The forward angle that S ' and X-axis form;

Be the angle of pitch, promptly line SS ' and the line A of S point in source at XOY face subpoint put in office ₁The angle of S ' formation,

For line SS ' and the line A of S point in source at XOY face subpoint put in office ₂The angle of S ' formation.

The phased ultrasound locating method of above-mentioned partial discharge of transformer, the covariance matrix of array data adopts 4 rank semi-invariants in the described MUSIC algorithm.

The phased ultrasound locating method of above-mentioned partial discharge of transformer, described phased array supersonic sensor are the planar structure of 16 array elements, 4 row * 4 row, and single array element is 4 * 4 * 16mm rectangular parallelepiped column, array element distance 5mm, and material is a piezoelectric ceramics.

A kind of phased ultrasound positioning system of partial discharge of transformer, constitute by phased array supersonic sensor, multi-channel high-speed data synchronous acquisition device and notebook computer, described phased array supersonic sensor is provided with two, the diverse location of being close to transformer case respectively, its output signal connects the input end of multi-channel high-speed data synchronous acquisition device through signal amplifier, and the signal output part of described multi-channel high-speed data synchronous acquisition device connects the input interface of notebook computer.

The phased array supersonic sensor that two diverse locations of transformer case are close in utilization of the present invention receives the ultrasonic broadband signal of shelf depreciation, and adopt the wideband array signal processing method directly the type local-discharge ultrasonic broadband signal to be handled, at the particular location that guarantees to determine under the prerequisite that tested transformer can be not impaired shelf depreciation, this method not only can be implemented online accurate location to transformer inside shelf depreciation, and used positioning system is simple in structure, and method is simple.

Description of drawings

The invention will be further described below in conjunction with accompanying drawing.

Fig. 1 is that direction finding cross bearing schematic diagram is put in office;

Fig. 2 is a TCT broadband focusing algorithm process flow diagram;

Fig. 3 is that the location algorithm process flow diagram is put in office;

Fig. 4 is 16 array element ultrasound phase-control array sensors;

Fig. 5 is the structural representation of Fig. 4;

Fig. 6 is that detection system constitutes synoptic diagram;

Fig. 7 is that the positioning experiment synoptic diagram is put in office;

Fig. 8 is experiment gained 16 passage time-domain filtering oscillograms;

Fig. 9 is a sensors A ₁Place's direction finding spectrogram;

Figure 10 is a sensors A ₂Place's direction finding spectrogram.

Each label is among the figure: A1, A2, phased array supersonic sensor; 1, cable; 2, gland nut; 3, stainless steel cover; 4, array element lead-in wire; 5, O-ring seal; 6, acoustic damping piece; 7, piezoelectricity array element; 8, Stainless Steel Shell; 9, silicon rubber filling; 10, stainless steel cuticula; 11, transformer; 12, signal amplifier; 13, multi-channel high-speed data synchronous acquisition device; 14, computer; 15, the source is put in office.

Each symbol is in the literary composition: A _β(f _j), the direction matrix; θ, signal source direction angle (source is put at projection of XOY face and X-axis forward angle in office); The signal source angle of pitch (source and its are put at projection of XOY face and Z axle forward angle in office); Θ, comprise the signal source direction angle θ and the angle of pitch

The parameter of information; The pre-estimation direction of β, signal source; f ₀, reference frequency is focusing center's frequency; f _j, the j segment data frequency; A (Θ), steering vector; σ ², noise power; λ _i, matrix eigenwert; X, data matrix; A, direction matrix; S, signal space data matrix; N, spatial noise data matrix; X (t), sampling duration are the data matrix of t; S (t), sampling duration are the signal space data matrix of t; N (t), sampling duration are the spatial noise data matrix of t; R, covariance matrix; e _i, matrix eigenvector;

The estimated value of matrix R; R _S, signal covariance matrix; R _N, noise covariance matrix; U _N, the noise characteristic vector matrix; U _S, the character vector of signals matrix; ∑ _S, the diagonal matrix that constitutes of big eigenwert; ∑ _N, the diagonal matrix that constitutes of little eigenwert; X (f _j), the j section receives the DFT conversion of data matrix; X (f _j), the j section receives the DFT conversion of data matrix; A _β(f ₀), the j section receives the DFT conversion of data direction matrix; S (f _j), the j section receives the DFT conversion of data-signal spatial data matrix; N (f _j), the j section receives the DFT conversion of data noise spatial data matrix; T _β(f _j), focussing matrix; E{}, statistical average are promptly expected; { } ^H, the conjugate transpose computing; || || _F, the Frobenius mould.{ } ^*, conjugate operation;

Kronecker is long-pending; || ||, norm.

Embodiment

Put the shortcoming of detection method at present conventional ultrasonic wave office, the present invention aims to provide a kind of positioning system and method thereof of wideband Array Signal Processing of partial discharge of transformer.

This invention adopts the phased array supersonic sensor to receive the ultrasonic broadband signal of shelf depreciation, form Array Model, and broadband focusing, arrowband direction finding and the realization of cross bearing scheduling algorithm in the application wideband Array Signal Processing algorithm provide effective reference to the detection and localization of shelf depreciation for accurately assessing the transformer partial discharge position and overhauling strategy.

For achieving the above object, concrete technical scheme provided by the invention is as follows:

1. the phased ultrasound positioning system of partial discharge of transformer.

This positioning system is constructed as follows: phased array supersonic sensor, signal amplifier (comprising charge amplifier, filter amplifier), multi-channel high-speed data synchronous acquisition device and notebook computer constitute.

The phased array supersonic sensor is the planar structure of 16 array elements, 4 row * 4 row, and single array element is 4 * 4 * 16mm rectangular parallelepiped column, array element distance 5mm, and material is a piezoelectric ceramics.

During the location, the phased array supersonic sensor is close to the shell of transformer, and each array element detects and obtains the type local-discharge ultrasonic signal, receives and form the planar array signal of 4 row * 4 row.

The array signal of 16 array elements connects 16 electric charges (voltage) amplifier respectively by cable, connects filter amplifier again, receives 16 channel data synchronous acquisition devices then, obtains the supersonic array time-domain signal of partial discharge of transformer.

2. partial discharge of transformer phased ultrasound locating method.

(1) partial discharge of transformer wideband supersonic array signal obtains.Adopt the phased array supersonic sensor of 4 row * 4 row directly to receive the shelf depreciation ultrasonic signal, and, on 16 passage high-speed data synchronous acquisition devices, obtain wideband supersonic array signal by after the filtering amplification from the transformer outer wall.

(2) wideband supersonic array signal processing algorithm and partial discharge of transformer location.

Adopt TCT (Two-sided Correlation Transformation) algorithm, improvement MUSIC (Multiple Signal Classification) algorithm and direction finding cross bearing principle in the wideband array signal space spectrum estimation theory to realize that office relaxes the focusing processing of band ultrasonic signal, direction of arrival is estimated and space orientation.Specific algorithm is as follows:

● the broadband focusing algorithm

The ultrasonic frequency that shelf depreciation produces mainly concentrates on 50kHz to 300kHz frequency range, and its crest frequency between 70kHz to 200kHz, is a broadband signal mainly.But MUSIC algorithm itself can only carry out the direction of arrival of narrow band signal to be estimated, the rigid ultrasonic signal that shelf depreciation is produced is lost as the spatial information (si) feature of enriching that the narrow band signal processing can make original signal have, and causes bearing accuracy not enough even can not realize.Therefore need at first to convert the signal data that receives to the narrow band signal data, carry out DOA in application narrow band signal Processing Algorithm and estimate.

The broadband focusing algorithm mainly is divided into two big classes, and the first kind is based on irrelevant Signal Processing method (ISM), and second class is based on the disposal route (CSM) of coherent signal.This class basic idea is that the data on nonoverlapping Frequency point in the frequency band are focused on the reference frequency point, obtains single-frequency point data covariance after the focusing, uses the narrow band signal Processing Algorithm again and carries out the DOA estimation.CSM class algorithm is compared with ISM class algorithm has the advantages that operand is little, estimated accuracy is high.Typical algorithm mainly contains: bilateral associated change method (TCT), gyrator space law (RSS), signal subspace converter technique (SST) etc.

The essence of above-mentioned algorithm all is to seek a focussing matrix T _β(f _j), the TCT algorithm is compared the focusing error minimum with other algorithm on the performance, best performance, and operand is moderate, and the data acquisition storage speed is suitable with the late time data processing speed, can satisfy the needs of handling real time data, therefore chooses TCT broadband focusing algorithm.

The focusing of wideband array signal is handled and is meant on the basis that guarantees the ultrasound wave broadband signal information that shelf depreciation produces, searching focussing matrix T _β(f _j), with the direction matrix A under the different frequency _β(f _j) transform to optimum reference frequency f ₀On, and then handle in conjunction with the arrowband algorithm.

Suppose that the broadband signal model is as follows: X (f _j)=A _β(f _j) S (f _j)+N (f _j) j=1,2 ..., J

Relation between a TCT algorithm utilization frequency between the noise free data is chosen focussing matrix.If focussing matrix is T _β(f _j), then have: T _β(f _j) A _β(f _j) S (f _j)=A _β(f ₀) S (f ₀)

Consider from receive data can't deterministic signal data vector S (f _j), its covariance matrix respectively can be got in the following formula both sides, abbreviation can get:

Wherein, P (f _j)=A _β(f _j) R _s(f _j) A _β ^H(f _j), signal covariance matrix R _s(f _j)=S (f _j) S ^H(f _j) consider the influence of error, following formula can further be improved to:

In addition, the focussing matrix in the following formula is added following normalization constraint:

As from the foregoing, the core of TCT algorithm is exactly under constraint condition, finds each Frequency point of broadband and optimum reference frequency f ₀Relation, T _β(f _j) separate for:

Wherein,

With

Be respectively to be listed as mutually orthogonal M * Metzler matrix, they are respectively span{P (f ₀) and span{P (f _j) orthogonal basis, promptly

With

Be respectively P ₀And P _jEigenvector.

Through the signal after the focussing matrix processing: T _β(f _j) X (f _j)=A _β(f ₀) S (f ₀)+N (f _j) j=1,2 ..., J

● improve the MUSIC algorithm

Suppose the signal (S in D far field ₁, S ₂..., S _d) incide on the array, wherein array is made up of M array element, and array element is spaced apart d, and the array output vector can be expressed as: X (t)=A (Θ) S (t)+N (t).

A (Θ)=[a wherein _i(Θ)],

I=1 ... D.Θ is for comprising the signal source direction angle θ and the angle of pitch

The parameter of information.The covariance matrix of array data is:

R＝E[XX ^H]＝AE[SS ^H]A ^H+σ ²I

＝AR _SA ^H+σ ²I

Wherein,

Be signal covariance matrix, AR _SA ^HIt is signal section.

R is carried out feature decomposition to be had:

$R=\underset{i=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\λ}}_i{e}_i{e_i}^H=U_s{\mathrm{\Σ}}_s{U}_s+U_n{\mathrm{\Σ}}_n{U_n}^H$

U wherein _sBe that the subspace that big eigenwert characteristic of correspondence vector is opened is called signal subspace, U _nBe to be called noise subspace by the subspace that the pairing proper vector of little eigenwert is opened, according to the feature decomposition theory as can be known, signal subspace and noise subspace are mutually orthogonal.Promptly

a ^H(Θ)U _n＝0

Traditional MUSIC algorithm just is being based on above-mentioned this character and is proposing, and the Estimation of Spatial Spectrum formula of MUSIC algorithm is:

$P_{\mathrm{MUSIC}}=\frac{1}{a^H\left(\mathrm{\Θ}\right)\widehat{\mathrm{Un}}{\widehat{\mathrm{Un}}}^{H}a\left(\mathrm{\Θ}\right)}$

Consider that the actual reception data matrix is time-limited, promptly the maximal possibility estimation of data covariance is

$\hat{R}=\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{XX}}^H$

In fact ask direction of arrival to realize with minimum optimization searching,

The essence of improving the MUSIC algorithm is that the covariance matrix of array data has adopted 4 rank semi-invariants, therefore compares with traditional MUSIC algorithm to have higher resolving power and estimated performance.Suppose that at non-Gaussian signal and Gaussian noise (including coloured noise) fourth order cumulant of array received data is down:

$C_{4k}(k_1,{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H2009101752527E0000031.png"\; state="\{\{state\}\}">k</figure-callout>}}_2,{\mathrm{<figure-callout\; id="3"\; label="k"\; filenames="H2009101752527E0000031.png,H2009101752527E0000051.png"\; state="\{\{state\}\}">k</figure-callout>}}_3,k_4)=\mathrm{cum}(x_{k1},{\mathrm{<figure-callout\; id="2"\; label="x\; k"\; filenames="H2009101752527E0000031.png"\; state="\{\{state\}\}">x</figure-callout>}}_k,{\mathrm{<figure-callout\; id="3"\; label="x\; k"\; filenames="H2009101752527E0000031.png,H2009101752527E0000051.png"\; state="\{\{state\}\}">x</figure-callout>}}_k^3,x_{\mathrm{<figure-callout\; id="4"\; label="k"\; filenames="H2009101752527E0000031.png"\; state="\{\{state\}\}">k</figure-callout>}4}^{*})$

$=E\left(x_{k1}{x}_{k2}{\mathrm{<figure-callout\; id="3"\; label="x\; k"\; filenames="H2009101752527E0000031.png,H2009101752527E0000051.png"\; state="\{\{state\}\}">x</figure-callout>}}_k^3{x}_{\mathrm{<figure-callout\; id="4"\; label="k"\; filenames="H2009101752527E0000031.png"\; state="\{\{state\}\}">k</figure-callout>}4}^{*}\right)-E\left(x_{k1}{\mathrm{<figure-callout\; id="3"\; label="x\; k"\; filenames="H2009101752527E0000031.png,H2009101752527E0000051.png"\; state="\{\{state\}\}">x</figure-callout>}}_k^3\right)E\left(x_{k2}{\mathrm{<figure-callout\; id="4"\; label="x\; k"\; filenames="H2009101752527E0000031.png"\; state="\{\{state\}\}">x</figure-callout>}}_k^4\right)-E\left(x_{k1}{\mathrm{<figure-callout\; id="4"\; label="x\; k"\; filenames="H2009101752527E0000031.png"\; state="\{\{state\}\}">x</figure-callout>}}_k^4\right)E\left(x_{k2}{\mathrm{<figure-callout\; id="3"\; label="x\; k"\; filenames="H2009101752527E0000031.png,H2009101752527E0000051.png"\; state="\{\{state\}\}">x</figure-callout>}}_k^3\right)-E\left(x_{k1}{x}_{k2}\right)E\left(x_{\mathrm{<figure-callout\; id="3"\; label="k"\; filenames="H2009101752527E0000031.png,H2009101752527E0000051.png"\; state="\{\{state\}\}">k</figure-callout>}3}^{*}{x}_{\mathrm{<figure-callout\; id="4"\; label="k"\; filenames="H2009101752527E0000031.png"\; state="\{\{state\}\}">k</figure-callout>}4}^{*}\right)$

For the array of M array element, the variable-value scope in the formula is 1≤k ₁, k ₂, k ₃, k ₄≤ M is therefore along with k ₁, k ₂, k ₃, k ₄Variation, total M ⁴Individual value.With this M ⁴Individual value is put into following M ²* M ²Matrix R ⁴In: R ⁴((k ₁-1) M+k ₃, (k ₂-1) M+k ₄)=C _4k(k ₁, k ₂, k ₃, k ₄)=B (Θ) C _SB ^H(Θ)

Be (the k of matrix ₁-1) M+k ₃Row and (k ₂-1) M+k ₄Train value be C _4k(k ₁, k ₂, k ₃, k ₄).

Separate between the signal source, following formula is carried out covariance matrix carry out feature decomposition, obtain the noise subspace of corresponding little eigenwert

Signal subspace U with big eigenwert _s=[λ ₁, λ ₂... λ _n], according to feature decomposition theory two sub spaces quadratures as can be known, utilize its orthogonality just to obtain improving the MUSIC algorithm.So the Estimation of Spatial Spectrum formula that improves the MUSIC algorithm is:

$P_{\mathrm{MUSIC}}=\frac{1}{{\left|\right|a\left(\mathrm{\&Theta;}\right)\&CircleTimes;a^{*}\left(\mathrm{\&Theta;}\right)U_n\left|\right|}^2}$

It is f that the signal that focuses on through the broadband is equivalent to centre frequency ₀Narrow band signal.Through the signal after the focussing matrix processing be: T _β(f _j) X (f _j)=A _β(f ₀) S (f ₀)+N (f _j) j=1,2 ..., J, it can be handled it with improving the MUSIC algorithm corresponding to narrow band signal X (t)=A (Θ) S (the t)+N (t) that improves in the MUSIC algorithm.U in the Estimation of Spatial Spectrum formula _nThe data that received by sensor are known quantity through algorithm process, the deflection θ to be measured and the angle of pitch

Be included among a (Θ).Improving the MUSIC algorithm asks type local-discharge ultrasonic signal direction of arrival to realize with minimum optimization searching.At first definite

Scope be (0 °-90 °), (0 °-180 °), angle intervals is got 0.1 ° (the more little calculated amount of angle intervals is big more, and estimated accuracy is high more) and is searched for then.This is to travel through calculating at one 2 dimensional plane, at this moment

Have 901 * 1801 combination angles, each group angle value and U _nBring the spectrum peak search formula into etc. known quantity, result of calculation is exported with the spectrogram form.The direction of arrival in source is put in the i.e. expression of the coordinate of peak correspondence office in the spectrogram.

Through obtaining one of them phased array supersonic sensors A with the focusing of last broadband, arrowband direction finding computing ₁Record office and put the azimuth angle theta and the angle of pitch in source

(definition θ: the position angle, the source is put at the line of XOY face subpoint and initial point and the forward angle of X-axis formation in office;

The angle of pitch, source and its forward angle in XOY face subpoint line and the formation of Z axle are put in office).Use same set of checkout equipment, with the phased array supersonic sensors A ₂Connect data acquisition unit, the data importing computing machine that receives, the step above repeating can obtain the phased array supersonic sensors A ₂Record office and put the position angle and the angle of pitch in source

Obtain two sensor offices of recording respectively and put the direction of arrival in source by twice broadband focusing, arrowband direction finding computing, in the locus of putting the source with direction finding cross bearing algorithm computation office.

● direction finding cross bearing algorithm

Direction finding cross bearing is to play a game simultaneously by two high-precision phased array supersonic sensors with putting the source target and carry out direction finding, the position of the directional data that records according to each phased array supersonic sensor and each array given in advance then, through triangulo operation, calculate out locus of putting the source.When the transformer inside office source of putting was positioned, we adopted two phased array supersonic sensors, were installed on the same oil tank wall of transformer its ultimate principle such as Fig. 1 respectively.

If phased array supersonic sensors A ₁, A ₂The plane, place is the XOY face, A ₁, A ₂Line is an X-axis, sets up rectangular coordinate system.Source S coordinate is put for (x, y z), play a game and put source S, A in office ₁, A ₂Two phased array supersonic sensors can obtain its four parameters altogether, and promptly the position angle and the angle of pitch of relative two the phased array supersonic sensors in source put in office

Only use three positions that can estimate target wherein.Below with

For example is analyzed.Get by geometric relationship:

Following formula is put in order, is got office and put the source coordinate:

Referring among Fig. 4, Fig. 5, the array element of 16 array element ultrasonic phase arrays is 4 row, 4 row square arrangement, array element distance 5mm, array element received signal centre frequency 150KHz.

Referring to Fig. 6, the phased ultrasound positioning system of partial discharge of transformer, by 2 phased array supersonic sensors, equidistant low cable, signal amplifier (voltage amplifier, filter amplifier), the multi-channel high-speed data synchronous acquisition device formation of decreasing, each unit installation connects as follows:

1. the installation of ultrasonic phase array

16 array element ultrasonic phase array design center frequency are 150KHz.Two ultrasonic phase array installation requirements are in same plane and reference array element point-blank.Two ultrasonic phase array spacings are far longer than self width.Array element distance 5mm.

In transformer inside, because insulating material character, design and the problem of making and the factor of impurity bubble, easily cause non-uniform electric, some place exists electric field too concentrated, this just very easily produces shelf depreciation, will select according to transformer built-in electrical insulation thin spot in the time of preliminary placement sensor.As shown in Figure 6, near the place of transformer built-in electrical insulation thin spot ultrasonic phase array is installed, is coupled with butter between ultrasonic phase array and the transformer case at the transformer outer wall.

2. connection detection system

Be output as quantity of electric charge weak output signal because the piezoelectric crystal that uses surpasses, must improve signal to noise ratio (S/N ratio) through amplifying the influence that could reduce undesired signal.And the carrying load ability of piezoelectric crystal is poor, requires pre-amplification circuit that bigger defeated people's impedance is arranged, and noise is low.Therefore 16 array elements connect 16 electric charges (voltage) amplifier respectively by cable, connect filter amplifier again, receive 16 passage high-speed data synchronous acquisition devices then, connect computing machine then.

3. data analysis and processing

With one 16 array element sensor is example, and what we can obtain in the experiment is 16 data files that 16 channel data synchronous acquisition devices are preserved.Construct thus three-dimensional data matrix x (m, n, t), m wherein, n, t are respectively the capable ordinal number of phased array supersonic sensor, the row ordinal number, the sampling time counts.Whole broadband signal is divided into the K section by the time that receives, and the data that respectively each array element received are carried out quick FFT conversion then, and each array element is carried out K time.(choosing of segments K value: for guaranteeing K segment data length unanimity, K at first will guarantee to be sampled the data sum and divide exactly; The K value is big more, and promptly the burnt performance of poly is good more more for segments, and operand also is doubled and redoubled simultaneously.Finally choose K=4 based on these 2.Both guarantee focusing performance, also considered data processing speed.)

Focus on and handle carry out TCT through the data output matrix after the FFT conversion, be divided into and be K time, each time all to focusing center's frequency.Optimum reference frequency f ₀Calculate (f according to the minimum accurate side of energy loss error ₀Choose; According to formula

Obtain focussing matrix T _β(f _j).The line focus matrix is handled, and broadband signal converts the treatable narrow band signal of down-stream to.According to the MUSIC algorithm principle, data matrix covariance is decomposed the signal subspace U that big eigenwert characteristic of correspondence vector is opened _s, the pairing proper vector of little eigenwert is opened into noise subspace U _nWhen the direction of arrival in source is put in the office of asking, at first definite

Scope be (0 °-90 °), (0 °-180 °).According to the angle intervals of determining, get step-length and search for for 0.1 ° then.At this moment Have 901 * 1801 combination angles, each group angle value and U _nBring the spectrum peak search formula into etc. known quantity, result of calculation is exported with the spectrogram form.The direction of arrival in source is put in the i.e. expression of the coordinate of peak correspondence office in the spectrogram.

Handle the data of two sensors respectively, the direction of arrival angle in source is put in the office of obtaining

The direction finding cross bearing principle that utilization is introduced above, the volume coordinate in source is put in calculating office.Algorithm flow such as Fig. 2.

Front end multiplying arrangement (charge/voltage amplifier) enlargement factor is 10-100 times, and back level multiplying arrangement (filter amplifier) enlargement factor is 1-200 times, regulates as required during test.During the inner generation of transformer shelf depreciation, its acoustic emission spectrum is than broad, and energy mostly concentrates on the 40KHz-200KHz frequency range, so the high-speed data acquiring device frequency band is selected 40KHz-250KHz, the setting sample frequency is 10M, and sampling length is 512K.Sending the data of coming to from capture card is binary number, through being converted into floating number, analyzes respectively on time domain and frequency domain.

Analysis on the time domain mainly is to obtain the time of arrival of shelf depreciation ultrasonic signal and number of times, by judging and the peak value of signal calculated obtains.Under laboratory condition, the noise level that collects signal is the millivolt level, the defeated artificial volt level of shelf depreciation ultrasonic signal, amplitude during discharge is apparently higher than noise signal, a discharge period is no more than 10 μ s, because sampling rate is 10MHz, institute thinks 100 points, therefore can obtain shelf depreciation time and number of times by calculating by the amplitude and the sequence number of these 100 points.

If on frequency domain, analyze the power spectrum of data owner analytic signal.The final TCT algorithm of using converts the shelf depreciation broadband signal to narrow band signal, uses the MMUSIC algorithm again and obtains signal and get direction of arrival, finally realizes partial discharge of transformer space orientation by dual sensor cross bearing.Location algorithm flow process such as Fig. 3 are put in office.

For verifying this present invention's correctness, carried out experimental study by Beijing high voltage and electromagnetic field key lab.The piezoelectricity transmitting probe that the source is put in the local office of simulation is a high-voltage pulse generator, the high-voltage pulse of output amplitude 4.5kV, pulsewidth 3 μ s, give off ultrasound wave in order to drive the piezoelectricity transmitting probe, can produce that amplitude is big, the ultrasonic signal of stable performance, and put it into and be full of mineral oil, be of a size of 100*100*120cm ³Fuel tank in, with shelf depreciation situation in the simulated oil.

Sensor array places the fuel tank outer wall, respectively at A ₁, A ₂The place carries out twice measurement to obtain direction of arrival, and A is set ₁Coordinate is (0,0,0), A ₂Coordinate is (100,0,0), and sets up three-dimensional cartesian coordinate system, as shown in Figure 7.Program control amplifilter of USB-13120pt01 type 16 passages and USB-11140pt10 type 16 port number device for picking that filtering amplification and data collector adopt Chengdu micrometering company to provide respectively, can realize parallel data acquisition, sample frequency is 10MHz, the filtering cutoff frequency is 40KHz to 250KHz, and signal amplification factor is 16 times.

Office is set, and to put the source coordinate be PD (50,60,80) cm, and record data trigger with electric signal, and fast umber of beats is 6400.A ₁Locate the received filtered waveform of ultrasonic phase array as shown in Figure 8, as space is limited A ₂Place's waveform slightly.

At first each passage time-domain signal is transformed to frequency domain, write then to focus on and handled and the direction finding algorithm routine, the office of obtaining puts the source direction of arrival and estimates spectrogram such as Fig. 9, shown in Figure 10, and its direction finding result is r ₁(47.8 °, 42.2 °) and r ₂(127.2 °, 42.4 °), putting the source coordinate by the direction finding intersection principle office of calculating again is PD ' (54.0,60.0,83.0) cm, its positioning result error r is 5.0cm.

Claims (6)

1. the phased ultrasound locating method of a partial discharge of transformer, it is characterized in that, the ultrasonic broadband signal that its employing places the phased array supersonic sensor office of acceptance source of putting of two diverse locations on the transformer to send, and formation Array Model, then, the broadband focusing algorithm of using in the wideband Array Signal Processing algorithm converts the broadband signal that two phased array supersonic sensors are received to narrow band signal, use arrowband direction finding algorithm again two narrow band signals are carried out the direction of arrival estimation respectively, use the particular location that the cross bearing algorithm is determined shelf depreciation at last.

2. according to the phased ultrasound locating method of the described partial discharge of transformer of claim 1, it is characterized in that concrete steps are as follows:

A, the ultrasonic broadband signal that adopts two phased array supersonic sensor office of acceptance sources of putting of being close to the transformer diverse location to send;

B, employing TCT broadband focusing algorithm are with the direction matrix A under the different frequency _β(f _j) transform to optimum reference frequency f ₀On:

Suppose that the broadband signal model is as follows: X (f _j)=A _β(f _j) S (f _j)+N (f _j) j=1,2 ..., J

S (f in the formula _j) be the data vector of signal, N (f _j) be that the j section receives data noise spatial data matrix,

Signal after then handling through focussing matrix is: T _β(f _j) X (f _j)=A _β(f ₀) S (f ₀)+N (f _j) j=1,2 ..., J

Wherein, Be focussing matrix,

With

Be respectively span{P (f ₀) and span{P (f _j) orthogonal basis, P (f _j)=A _β(f _j) R _s(f _j) A _β ^H(f _j);

The source coordinate system is put in c, foundation office, establishes the phased array supersonic sensors A ₁, A ₂The plane, place is the XOY face, A ₁, A ₂Line is an X-axis, with A ₁For initial point is set up rectangular coordinate system, then office's coordinate of putting source S for (x, y, z);

D, adopt the MUSIC algorithm respectively two narrow band signals to be carried out direction of arrival to estimate, obtain the office that two phased array supersonic sensors record and put the position angle and the angle of pitch in source;

The position angle in source and the position of the angle of pitch and each phased array supersonic sensor are put in e, the office that records according to each phased array supersonic sensor, calculate out volume coordinate position of putting the source and are:

Wherein, θ ₁, θ ₂Be the position angle, θ ₁For source S point is put at XOY face subpoint S ' and A in office ₁Line A ₁The forward angle that S ' and X-axis form; θ ₂For source S point is put at XOY face subpoint S ' and A in office ₂Line A ₂The forward angle that S ' and X-axis form;

Be the angle of pitch, promptly line SS ' and the line A of S point in source at XOY face subpoint put in office ₁The angle of S ' formation, For line SS ' and the line A of S point in source at XOY face subpoint put in office ₂The angle of S ' formation.

3. according to the phased ultrasound locating method of the described partial discharge of transformer of claim 2, it is characterized in that the covariance matrix of array data adopts 4 rank semi-invariants in the described MUSIC algorithm.

4. according to the phased ultrasound locating method of the described partial discharge of transformer of claim 3, it is characterized in that described phased array supersonic sensor is the planar structure of 16 array elements, 4 row * 4 row, single array element is 4 * 4 * 16mm rectangular parallelepiped column, array element distance 5mm, material is a piezoelectric ceramics.

5. partial discharge of transformer phased ultrasound positioning system, it is characterized in that, it is made of phased array supersonic sensor, multi-channel high-speed data synchronous acquisition device (13) and notebook computer (14), described phased array supersonic sensor is provided with two, the diverse location of being close to transformer (11) shell respectively, its output signal connects the input end of multi-channel high-speed data synchronous acquisition device (13) through signal amplifier (12), and the signal output part of described multi-channel high-speed data synchronous acquisition device (13) connects the input interface of notebook computer (14).

6. partial discharge of transformer phased ultrasound positioning system according to claim 5, it is characterized in that described phased array supersonic sensor is the planar structure of 16 array elements, 4 row * 4 row, single array element is 4 * 4 * 16mm rectangular parallelepiped column, array element distance 5mm, material is a piezoelectric ceramics.

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