A hotspot positioning method for ultrasonic phased array of electric power equipment

Abstract

The present invention relates to the field of ultrasonic detection technology, and specifically to a method for hotspot positioning of an ultrasonic phased array of electric power equipment, comprising determining a focal area to be scanned based on the winding structure inside the electric power equipment; establishing a three-dimensional coordinate system, setting the focal coordinates, and determining an excitation delay based on the focal coordinates and the coordinates of each array element; controlling the ultrasonic phased array sensor to emit ultrasonic waves at a pulse period based on the excitation delay, and receiving reflected sound wave signals; calculating the time delay difference of the ultrasonic signals of each array element in each scanning area; constructing an objective function based on the spatial geometric relationship between the array element coordinates of the ultrasonic phased array sensor and the focal area and the time delay difference, performing hotspot positioning through particle swarm optimization to determine the minimized objective function value, and performing hotspot coordinate positioning of the electric power equipment. By controlling the excitation delay of each array element of the ultrasonic phased array sensor, the sound beam emitted by each array element forms a focused sound field, constructing the objective function, and achieving hotspot positioning through particle swarm optimization.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic detection technology, and in particular to a hotspot positioning method for an ultrasonic phased array of electric power equipment. Background Art

[0002] Accurately assessing the insulation level of large-scale power equipment (transformers, generators, and GIS, etc.) is the basis for reliable power grid operation. However, existing technologies such as oil chromatography, partial discharge, infrared, and ultraviolet detection all focus on post-discharge or creepage detection. These technologies are characterized by a relatively delayed detection time, a lack of effective early warning signals, and a failure to meet the requirements of frontline operation and maintenance.

[0003] As local defects develop and eventually break down, discharge or current loss can occur, generating heat and forming localized hot spots. Deformation of key parts within power equipment or loss of insulation can also cause electric field distortion, leading to discharge and heating. Therefore, temperature monitoring of hot spots in power equipment is an effective means of defect diagnosis and fault warning. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method for locating hotspots of electric power equipment using an ultrasonic phased array, comprising:

[0005] An ultrasonic phased array sensor is installed on the outer wall of a box on one side of the power equipment, the spacing between the elements of the ultrasonic phased array sensor is determined, and the operating frequency of the ultrasonic phased array sensor is set;

[0006] According to the winding structure inside the power equipment, the focus area to be scanned is determined; with the array center of the ultrasonic phased array sensor as the origin, a three-dimensional coordinate system is established, and the focus coordinates are set ( x f ，y f ，z f ); Determine the excitation delay based on the focal coordinates and the coordinates of each array element;

[0007] Based on the excitation delay, the ultrasonic phased array sensor is controlled to emit ultrasonic waves in a pulse period and receive the reflected sound wave signals. The ultrasonic phased array sensor is translated and scanned along the outer wall of the box based on the step size until the focus area to be detected is completely covered, and all the reflected sound wave signals are obtained.

[0008] Preprocessing the acquired acoustic wave signals, performing beamforming on the preprocessed acoustic wave signals, and calculating the time delay difference of the ultrasonic signal of each array element in each scanning area;

[0009] The objective function is constructed based on the spatial geometric relationship and time delay difference between the array element coordinates and the focal area of ​​the ultrasonic phased array sensor. The hotspot coordinates of the power equipment are located by minimizing the objective function value through particle swarm optimization.

[0010] The objective function is:

[0011] ,

[0012] Where, ( x i ,y i ,z i ) indicates the i The coordinates of the array elements; ( x,y,z ) represents the coordinates of the hotspot to be located; v Indicates the medium propagation speed of ultrasonic waves; τ ij Represents array element i and Zhenyuan j The delay difference.

[0013] The hotspot positioning by particle swarm optimization is performed to determine the minimized objective function value, specifically:

[0014] Initialize the particle swarm and set the maximum number of iterations; randomly generate candidate coordinates representing hot spots ( x,y,z );

[0015] Calculate the objective function value corresponding to the candidate coordinate according to the objective function;

[0016] Update the particle speed and position to move it to the area with smaller objective function value;

[0017] If the number of iterations reaches the maximum number of iterations or the objective function value approaches 0, the particle swarm convergence coordinate value is determined, which is the hotspot coordinate located in the scanning area.

[0018] The hotspot coordinate positioning of the electric power equipment further includes aggregating the hotspot coordinates obtained by positioning different scanning areas, and correcting each hotspot coordinate by weighted average to obtain a final hotspot position.

[0019] In order to prevent the influence of noise on the sound wave signal, the acquired sound wave signal is preprocessed, including performing empirical mode decomposition on the sound wave signal and screening the IMF component with high correlation with the original signal.

[0020] The hotspot positioning method of the ultrasonic phased array for electric power equipment further includes performing Fourier transform on the denoised signal to extract features, wherein the extracted features include arrival time difference, amplitude peak value and main frequency offset.

[0021] The pre-processed acoustic wave signal is beamformed, and the acoustic wave signal of each array element is weightedly superimposed to enhance the target direction signal:

[0022] ,

[0023] in, y(t) It is the enhanced target direction signal after beamforming; w i represents the weighting coefficient; M is the number of array elements; x i (t-τ i ) Indicates the i The reflected ultrasonic signal obtained by each array element.

[0024] In order to accurately locate the hotspot inside the box, the ultrasonic phased array sensor is translated and scanned along the outer wall of the box based on the step length. The specific method is as follows:

[0025] Divide the outer wall of the box where the ultrasonic phased array sensor is set into regions, and set nodes along the x-direction and y-direction according to preset step sizes;

[0026] Draw lines parallel to the y axis for the nodes in the x direction, and draw lines parallel to the x axis for the nodes in the y direction to divide the outer wall of the box into several scanning areas;

[0027] Move the ultrasonic phased array sensor to each scanning area to scan, and obtain the reflected sound wave signal received by each array element in each scanning area of ​​the outer wall of the box;

[0028] The ultrasonic phased array sensor is placed on the outer wall of other boxes of the power equipment, and the above operation is repeated until all the outer walls of the boxes are scanned. The scanning is then ended.

[0029] In a specific embodiment, the power equipment includes a transformer, a generator, and an oil-immersed reactor.

[0030] Beneficial effects: The present invention is a method for hotspot positioning of an ultrasonic phased array of electric power equipment. According to the internal structural characteristics of different electric power equipment, by controlling the excitation delay of each array element of the ultrasonic phased array sensor, the sound beam emitted by each array element produces constructive interference at a set depth, forming a focused sound field, which can effectively avoid false detection and missed detection caused by sensor installation position restrictions, fixed focus, and limited angle, and realize efficient and accurate local hotspot positioning. Hotspot positioning can also be customized according to the internal structural characteristics of different electric power equipment. The present invention is suitable for electric power equipment with various complex structures. At the same time, the acquired acoustic wave signal is preprocessed and beamformed, and the delay difference is calculated. The objective function is constructed and the hotspot positioning is realized through particle swarm optimization, which improves the accuracy and efficiency of hotspot positioning. DETAILED DESCRIPTION

[0031] Exemplary embodiments of the present disclosure will be described in more detail below.

[0032] This embodiment provides a method for locating hotspots of electric power equipment using an ultrasonic phased array. The specific implementation steps are as follows:

[0033] Step 1: Install an ultrasonic phased array sensor on the outer wall of a box on one side of the power equipment, determine the spacing between each element of the ultrasonic phased array sensor, and set the operating frequency of the ultrasonic phased array sensor;

[0034] This application uses a linear ultrasonic line-controlled array sensor, and the array element spacing is set according to the wavelength. d=λ / 2. It can avoid grating lobe interference.

[0035] The power equipment includes transformers, generators and oil-immersed reactors. The basic structure is composed of windings, oil tanks and other devices. By setting the operating frequency of the ultrasonic phased array sensor to 50kHz-200kHz, the low-frequency penetration is strong and suitable for the oil-immersed environment of the power equipment box.

[0036] Step 2: Determine the focus area to be scanned based on the winding structure inside the power equipment; establish a three-dimensional coordinate system with the array center of the ultrasonic phased array sensor as the origin, and set the focus coordinates ( x f ，y f ，z f ); Determine the excitation delay based on the focal coordinates and the coordinates of each array element;

[0037] With the array center of the ultrasonic phased array sensor as the origin, a three-dimensional coordinate system is established to determine the three-dimensional coordinates of each array element ( x i ，y i ，0), and assume the focus coordinates based on the focus area to be scanned.

[0038] The excitation delay is determined based on the focal coordinates and the coordinates of each array element so that the ultrasonic signal of each array element is focused at the focal area. The excitation delay is:

[0039] ,

[0040] in, v Indicates the speed of sound.

[0041] Step 3: Control the ultrasonic phased array sensor to emit ultrasonic waves at a pulse period based on the excitation delay and receive the reflected sound wave signals; translate the ultrasonic phased array sensor along the outer wall of the box based on the step size until the focal area to be detected is completely covered, and obtain all the scanned reflected sound wave signals;

[0042] The ultrasonic phased array sensor is controlled by a pulse drive signal, driving it to emit ultrasonic waves at a fixed pulse period. Simultaneously, the phase of each element's transmitted ultrasound waves is controlled based on the excitation delay, allowing each element of the ultrasonic phased array sensor to simultaneously focus on a focal area based on different excitation delays.

[0043] The specific method of performing translational scanning of the ultrasonic phased array sensor along the outer wall of the box based on the step length is as follows:

[0044] Divide the outer wall of the box where the ultrasonic phased array sensor is set into regions, and set nodes along the x-direction and y-direction according to preset step sizes;

[0045] Draw lines parallel to the y axis for the nodes in the x direction, and draw lines parallel to the x axis for the nodes in the y direction to divide the outer wall of the box into several scanning areas;

[0046] Move the ultrasonic phased array sensor to each scanning area to scan, and obtain the reflected sound wave signal received by each array element in each scanning area of ​​the outer wall of the box;

[0047] The ultrasonic phased array sensor is placed on the outer wall of other boxes of the power equipment, and the above operation is repeated until all the outer walls of the boxes are scanned. The scanning is then ended.

[0048] Step 4: pre-process the acquired acoustic wave signals, perform beamforming on the pre-processed acoustic wave signals, and calculate the time delay difference of the ultrasonic signal of each array element in each scanning area;

[0049] The reflected ultrasonic signal obtained by the single array element is:

[0050] ,

[0051] in, s(t) To transmit ultrasonic signals, n i (t) is Gaussian white noise.

[0052] The acquired acoustic wave signal is preprocessed, including empirical mode decomposition of the acoustic wave signal and screening of the IMF components with high correlation with the original signal. Dynamic threshold wavelet denoising is used for the noisy IMF components, and the threshold function is:

[0053] ,

[0054] in, α is the regulating factor, w j,k are the initial wavelet coefficients, q is the threshold, , represents the noise variance, and N is the signal length.

[0055] Fourier transform is performed on the denoised signal to extract features, where the extracted features include arrival time difference, amplitude peak value and main frequency offset.

[0056] Beamforming is performed on the pre-processed acoustic wave signal, and the acoustic wave signals of each array element are weighted and superimposed to enhance the target direction signal:

[0057] ,

[0058] in, y(t) It is the enhanced target direction signal after beamforming; w i Represents the weighting coefficient, which is used to control the superposition weight of each array element signal; M is the number of array elements; x i (t-τ i ) Indicates the i The reflected ultrasonic signal obtained by each array element.

[0059] Based on the target direction signal and the transmitted signal of each array element, the delay difference is calculated by generalized cross correlation (GCC) The generalized cross-correlation function is:

[0060] ,

[0061] in, R ij ( τ ) indicates the i The array element and the j The generalized cross-correlation function value of each array element; τ For time delay; X i ( ω ) indicates the i The array elements obtain the Fourier transform of the signal; Indicates the j The array element obtains the complex conjugate of the Fourier transform of the signal; ω is the angular frequency; e jωτ Represents a complex exponential term.

[0062] Step 5: Based on the spatial geometric relationship between the array element coordinates of the ultrasonic phased array sensor and the focal area and the time delay difference, an objective function is constructed, and hotspot positioning is performed through particle swarm optimization to determine the minimized objective function value, and the hotspot coordinates of the power equipment are positioned;

[0063] For each scanning area, the objective function is constructed based on the spatial geometric relationship between the coordinates of each element of the ultrasonic phased array sensor and the focal area and the time delay difference:

[0064] ,

[0065] The hotspot location is determined by particle swarm optimization to minimize the objective function value. The specific method is as follows:

[0066] Initialize the particle swarm and set the maximum number of iterations; randomly generate candidate coordinates representing hot spots ( x,y,z );

[0067] Calculate the objective function value corresponding to the candidate coordinate according to the objective function;

[0068] Update the particle speed and position to move it to the area with smaller objective function value;

[0069] If the number of iterations reaches the maximum number of iterations or the objective function value approaches 0, the particle swarm convergence coordinate value is determined, which is the hotspot coordinate located in the scanning area.

[0070] The hotspot coordinates obtained from different scanning areas are summarized, and the weighted average is used to correct the hotspot coordinates to obtain the final hotspot position.

Claims

1. A method for locating hotspots of an ultrasonic phased array for electric power equipment, characterized in that: include: An ultrasonic phased array sensor is installed on the outer wall of a box on one side of the power equipment, the spacing between the elements of the ultrasonic phased array sensor is determined, and the operating frequency of the ultrasonic phased array sensor is set; Determine the focus area to be scanned based on the winding structure inside the power equipment; With the array center of the ultrasonic phased array sensor as the origin, a three-dimensional coordinate system is established, and the focus coordinates are set ( x f ,y f ,z f ); Determine the excitation delay based on the focal coordinates and the coordinates of each array element; Based on the excitation delay, the ultrasonic phased array sensor is controlled to emit ultrasonic waves in a pulse period and receive the reflected sound wave signals. The ultrasonic phased array sensor is translated and scanned along the outer wall of the box based on the step size until the focus area to be detected is completely covered, and all the reflected sound wave signals are obtained. Preprocessing the acquired acoustic wave signals, performing beamforming on the preprocessed acoustic wave signals, and calculating the time delay difference of the ultrasonic signal of each array element in each scanning area; Based on the spatial geometric relationship and time delay difference between the array element coordinates and the focal area of ​​the ultrasonic phased array sensor, an objective function is constructed. The hotspot coordinates of the power equipment are located by minimizing the objective function value through particle swarm optimization. The objective function is: Where, ( x i ,y i ,z i ) indicates the i The coordinates of the array elements; ( x,y,z ) represents the coordinates of the hotspot to be located; v Indicates the medium propagation speed of ultrasonic waves; τ ij Represents array element i and Zhenyuan j The delay difference; The hotspot is located by particle swarm optimization to determine the minimized objective function value, specifically: Initialize the particle swarm and set the maximum number of iterations; randomly generate candidate coordinates representing hot spots ( x,y,z ); Calculate the objective function value corresponding to the candidate coordinate according to the objective function; Update the particle speed and position to move it to the area with smaller objective function value; If the number of iterations reaches the maximum number of iterations or the objective function value approaches 0, the particle swarm convergence coordinate value is determined, which is the hotspot coordinate located in the scanning area.

2. The hotspot location method for ultrasonic phased array of electric power equipment according to claim 1, characterized in that: The hotspot coordinate positioning of the electric power equipment further includes aggregating the hotspot coordinates obtained by positioning different scanning areas, and correcting each hotspot coordinate by weighted average to obtain a final hotspot position.

3. The hotspot location method for ultrasonic phased array of electric power equipment according to claim 1, characterized in that: The preprocessing of the acquired acoustic wave signal includes performing empirical mode decomposition on the acoustic wave signal and screening IMF components with high correlation with the original signal.

4. The method for hotspot location of electric power equipment using ultrasonic phased array according to claim 1, characterized in that: The method also includes performing Fourier transform on the denoised signal to extract features, where the extracted features include arrival time difference, amplitude peak value and main frequency offset.

5. The hotspot location method for ultrasonic phased array of electric power equipment according to claim 1, characterized in that: The pre-processed acoustic wave signal is beamformed, and the acoustic wave signal of each array element is weightedly superimposed to enhance the target direction signal: in, y(t) It is the enhanced target direction signal after beamforming; w i represents the weighting coefficient; M is the number of array elements; x i (t- τ i ) Indicates the i The reflected ultrasonic signal obtained by each array element.

6. The method for hotspot location of electric power equipment using ultrasonic phased array according to claim 1, characterized in that: The specific method of performing translational scanning of the ultrasonic phased array sensor along the outer wall of the box based on the step length is as follows: Divide the outer wall of the box where the ultrasonic phased array sensor is set into regions, and set nodes along the x-direction and the y-direction according to preset step sizes; Draw lines parallel to the y axis for the nodes in the x direction, and draw lines parallel to the x axis for the nodes in the y direction to divide the outer wall of the box into several scanning areas; Move the ultrasonic phased array sensor to each scanning area to scan, and obtain the reflected sound wave signal received by each array element in each scanning area of ​​the outer wall of the box; The ultrasonic phased array sensor is placed on the outer wall of other boxes of the power equipment, and the above operation is repeated until all the outer walls of the boxes are scanned, and the scanning is ended.

7. The method for hotspot location of electric power equipment using ultrasonic phased array according to claim 1, characterized in that: The power equipment includes transformers, generators, and oil-immersed reactors.

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