Electric power equipment ultrasonic phase control array hot spot positioning method

Abstract

The invention relates to the technical field of ultrasonic detection, in particular to an electric power equipment ultrasonic phase control array hot spot positioning method, which comprises the following steps: determining a focus area to be scanned according to a winding structure in electric power equipment; establishing a three-dimensional coordinate system, setting a focus coordinate, and determining excitation delay based on the focus coordinate and the coordinate of each array element; controlling the ultrasonic phased array sensor to emit ultrasonic waves in a pulse period based on excitation delay, and receiving reflected sound wave signals; calculating to obtain the delay inequality of each array element ultrasonic signal of each scanning area; an objective function is constructed based on a spatial geometrical relationship between array element coordinates of the ultrasonic phased array sensor and a focus area and delay inequality, hot spot positioning is performed through particle swarm optimization to determine a minimum objective function value, and hot spot coordinate positioning of the electric power equipment is performed. By controlling the excitation delay of each array element of the ultrasonic phased array sensor, acoustic beams emitted by each array element form a focused sound field, a target function is constructed, and hotspot positioning is realized through particle swarm optimization.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic detection, and particularly to an ultrasonic phased array hot spot location method for power equipment. Background Art

[0002] Accurate assessment of the insulation level of large power equipment (such as transformers, generators, and GIS) is the basis for the reliable operation of the power grid. However, existing technologies such as oil chromatography, partial discharge, infrared, and ultraviolet all belong to the process detection after the occurrence of discharge or creepage. The detection time is relatively lagged, lacking effective warning signals and time, and cannot meet the requirements of on-site operation and maintenance.

[0003] During the process of gradual development of local defects until breakdown, discharge or current loss will also occur, generating heat to form local overheating points; deformation of key parts inside power equipment or detachment of insulating parts will cause electric field distortion, resulting in the occurrence of discharge and heat generation. Therefore, the temperature monitoring of hot spots in power equipment is an effective means for defect diagnosis and fault warning. Summary of the Invention

[0004] To solve the above problems, the present invention provides an ultrasonic phased array hot spot location method for power equipment, including: Setting an ultrasonic phased array sensor on the outer wall of the box on one side of the power equipment, determining the element pitch of the ultrasonic phased array sensor, and setting the operating frequency of the ultrasonic phased array sensor; According to the winding structure inside the power equipment, determining the focus area to be scanned; taking the array center of the ultrasonic phased array sensor as the origin, establishing a three-dimensional coordinate system, and setting the focus coordinates ( x f ，y f ，z f ); determining the excitation delay based on the focus coordinates and the coordinates of each element; Controlling the ultrasonic phased array sensor to emit ultrasonic waves at a pulse period based on the excitation delay, and receiving the reflected acoustic wave signals; translating and scanning the ultrasonic phased array sensor along the outer wall of the box based on a step size until the entire focus area to be detected is completely covered, and obtaining all the scanned and reflected acoustic wave signals; Preprocessing the obtained acoustic wave signals, performing beamforming on the preprocessed acoustic wave signals, and calculating the time delay differences of the ultrasonic wave signals of each element in each scanned area; Constructing an objective function based on the spatial geometric relationship between the element coordinates of the ultrasonic phased array sensor and the focus area and the time delay differences, and performing hot spot location through particle swarm optimization to determine the minimum value of the objective function value, and performing hot spot coordinate location of the power equipment.

[0005] The objective function is: , In the formula, ( x i ,y i ,z i ) represents the coordinates of the i th array element; ( x, y, z ) represents the coordinates of the hot spot position to be located; v represents the medium propagation speed of ultrasonic waves; τ ij represents the array element i and the array element j time delay difference.

[0006] The hot spot positioning by particle swarm optimization to determine the minimum objective function value is specifically as follows: Initialize the particle swarm and set the maximum number of iterations; randomly generate candidate coordinates ( x, y, z ) representing the hot spot; Calculate the objective function value corresponding to the candidate coordinates according to the objective function; Update the particle velocity and position to move it to the area with a smaller objective function value; If the number of iterations reaches the maximum number of iterations or the objective function value approaches 0, determine the convergence coordinate value of the particle swarm, which is the hot spot coordinates for positioning in the scanning area.

[0007] The hot spot coordinate positioning of the power equipment also includes summarizing the hot spot coordinates obtained by positioning in different scanning areas and correcting each hot spot coordinate using weighted averaging to obtain the final hot spot position.

[0008] To prevent the influence of noise on the acoustic wave signal, the acquired acoustic wave signal is preprocessed, including performing empirical mode decomposition on the acoustic wave signal and screening the IMF components with high correlation with the original signal.

[0009] The ultrasonic phased array hot spot positioning method for the power equipment also includes extracting features by performing Fourier transform on the denoised signal, and the extracted features include time difference of arrival, amplitude peak, and main frequency shift.

[0010] Performing beamforming on the preprocessed acoustic wave signal, and weighted superposition of the acoustic wave signals of each array element to enhance the target direction signal is: , where y(t) 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 ) indicating the reflected ultrasonic signal obtained by the i th array element.

[0011] In order to accurately locate the hot spots inside the box, the ultrasonic phased array sensor is translated and scanned along the outer wall of the box based on a step size. The specific method 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 y - direction according to the preset step size; Draw parallel lines to the y - axis for the nodes in the x - direction and parallel lines to the x - axis for the nodes in the y - direction for division, and divide the outer wall of the box into several scanning regions; Move the ultrasonic phased array sensor to each scanning region for scanning, and obtain the reflected acoustic wave signals received by each array element in each scanning region of the outer wall of the box; Set the ultrasonic phased array sensor on the outer walls of other boxes of the power equipment, and repeat the above operations until all the outer walls of the boxes are scanned completely, and then end the scanning.

[0012] In the specific implementation manner, the power equipment includes transformers, generators, and oil - immersed reactors.

[0013] Beneficial effects: The present invention is a method for locating hot spots of an ultrasonic phased array of power equipment. According to the internal structural characteristics of different power equipment, by controlling the excitation delay of each array element of the ultrasonic phased array sensor, the sound beams emitted by each array element generate constructive interference at a set depth, forming a focused sound field. It can effectively avoid false detections and missed detections caused by limitations in the sensor installation position, fixed focal points, and limited angles, and achieve efficient and accurate local hot - spot positioning. Moreover, it can perform customized hot - spot positioning according to the internal structural characteristics of different power equipment. The present invention is applicable to power equipment with various complex structures; at the same time, the acquired acoustic wave signals are pre - processed and beam - formed, and the time - delay difference is calculated. A target function is constructed and hot - spot positioning is achieved through particle swarm optimization, improving the accuracy and efficiency of hot - spot positioning. Specific implementation manner

[0014] The following will describe the exemplary embodiments of the present disclosure in more detail.

[0015] This embodiment provides a method for locating hot spots of an ultrasonic phased array of power equipment. The specific implementation steps are as follows: Step 1: Set the ultrasonic phased array sensor on the outer wall of one side of the power equipment, determine the pitch of each array element of the ultrasonic phased array sensor, and set the operating frequency of the ultrasonic phased array sensor; This application uses a linear ultrasonic wire - controlled array sensor, and the pitch of the array elements is set to d = λ / 2 according to the wavelength, which can avoid grating lobe interference.

[0016] The power equipment includes transformers, generators and oil-immersed reactors. Their basic structures are all composed of devices such as windings and oil tanks. By setting the operating frequency of the ultrasonic phased array sensor to 50 kHz - 200 kHz, the low frequency has strong penetrability and is suitable for the oil-immersed environment of the power equipment box.

[0017] Step 2: Determine the focus area to be scanned according to the winding structure inside the power equipment; taking the array center of the ultrasonic phased array sensor as the origin, establish a three-dimensional coordinate system, and set the focus coordinates ( x f ，y f ，z f ); Determine the excitation delay based on the focus coordinates and the coordinates of each element; Taking the array center of the ultrasonic phased array sensor as the origin, establish a three-dimensional coordinate system, and respectively determine the three-dimensional coordinates of each element ( x i ，y i ， 0), and assume the focus coordinates according to the focus area to be scanned.

[0018] Determine the excitation delay based on the focus coordinates and the coordinates of each element, so that the ultrasonic signals of each element are focused at the focus area. The excitation delay is: , where v represents the speed of sound.

[0019] Step 3: Control the ultrasonic phased array sensor to emit ultrasonic waves with a pulse period based on the excitation delay, and receive the reflected acoustic signals; translate and scan the ultrasonic phased array sensor along the outer wall of the box based on a step size until the entire focus area to be detected is completely covered, and obtain all the scanned and reflected acoustic signals; Control the ultrasonic phased array sensor through a pulse drive signal to drive the ultrasonic phased array sensor to emit ultrasonic waves outward with a fixed pulse period. At the same time, control the phase of the ultrasonic waves emitted by each element based on the excitation delay, so that each element of the ultrasonic phased array sensor can be focused on the focus area simultaneously according to different excitation delays.

[0020] The method of translating and scanning the ultrasonic phased array sensor along the outer wall of the box based on a step size is as follows: Divide the area of the outer wall of the box where the ultrasonic phased array sensor is set, and set nodes along the x direction and y direction according to the preset step size; Draw parallel lines to the y-axis for the nodes in the x-direction and parallel lines to the x-axis for the nodes in the y-direction to divide the outer wall of the box into several scanning regions; Move the ultrasonic phased array sensor to each scanning region for scanning to obtain the reflected acoustic wave signals received by each element in each scanning region of the outer wall of the box; Set the ultrasonic phased array sensor on the outer walls of other boxes of the power equipment, and repeat the above operations until all the outer walls of the boxes are scanned, and then end the scanning.

[0021] Step Four: Preprocess the obtained acoustic wave signals. By performing beamforming on the preprocessed acoustic wave signals, calculate the time delay differences of the ultrasonic wave signals of each element in each scanning region; The reflected ultrasonic wave signal obtained by a single element is: , where s(t) is the transmitted ultrasonic wave signal, n i (t) is Gaussian white noise.

[0022] Preprocess the obtained acoustic wave signals, including performing empirical mode decomposition on the acoustic wave signals and screening the IMF components with high correlation with the original signal. For the noisy IMF components, use dynamic threshold wavelet denoising, and the threshold function is: , where α is the adjustment factor, w j,k is the initial wavelet coefficient, q is the threshold, , represents the noise variance, and N is the signal length.

[0023] Perform Fourier transform on the denoised signal to extract features. The extracted features include time difference of arrival, amplitude peak, and main frequency offset.

[0024] Perform beamforming on the preprocessed acoustic wave signals, and perform weighted superposition on the acoustic wave signals of each element to enhance the target direction signal as: , where y(t) is the enhanced target direction signal after beamforming; w i represents the weighting coefficient, which is used to control the superposition weight of each element signal; M is the number of elements; x i (t - τ i ) represents thei The reflected ultrasonic signals obtained by each array element.

[0025] Based on the target direction signal and the transmission signals of each array element, calculate the time delay difference through generalized cross-correlation (GCC). The generalized cross-correlation function is: , where, R ij ( τ ) represents the generalized cross-correlation function value between the i th array element and the j th array element; τ is the time delay; X i ( ω ) represents the Fourier transform of the signal obtained by the i th array element; represents the complex conjugate of the Fourier transform of the signal obtained by the j th array element; ω is the angular frequency; e jωτ represents the complex exponential term.

[0026] Step Five: Based on the spatial geometric relationship between the array element coordinates of the ultrasonic phased array sensor and the focal region and the time delay difference, construct an objective function, and perform hot spot localization through particle swarm optimization to determine the minimum value of the objective function, and perform hot spot coordinate localization of the power equipment; For each scanning area, based on the spatial geometric relationship between the array element coordinates of the ultrasonic phased array sensor and the focal region and the time delay difference, construct the objective function as: , Perform hot spot localization through particle swarm optimization to determine the minimum value of the objective function. The specific method is: Initialize the particle swarm and set the maximum number of iterations; randomly generate candidate coordinates representing the hot spot ( x, y, z ); Calculate the objective function value corresponding to the candidate coordinates according to the objective function; Update the particle velocity and position to make it move to the area with a smaller objective function value; If the number of iterations reaches the maximum number of iterations or the objective function value approaches 0, then determine the convergence coordinate value of the particle swarm, which is the hot spot coordinate located in this scanning area.

[0027] Summarize the hot spot coordinates located in different scanning areas, and use weighted average to correct each hot spot coordinate to obtain the final hot spot position.

Claims

1. A method for locating hotspots of an ultrasonic phased array for electric power equipment, characterized in that: Including: Set an ultrasonic phased array sensor on the outer wall of the box on one side of the power equipment, determine the element spacing of the ultrasonic phased array sensor, and set the operating frequency of the ultrasonic phased array sensor; Determine the focus area to be scanned according to the winding structure inside the power equipment; Taking the center of the array of ultrasonic phased array sensors as the origin, a three-dimensional coordinate system is established, and the focal point coordinates are set ( x f ，y f ，z f ); Based on the focal point coordinates and the coordinates of each array element, the excitation delay is determined; Based on the excitation delay, control the ultrasonic phased array sensor to emit ultrasonic waves with a pulse period and receive the reflected acoustic signals; translate and scan the ultrasonic phased array sensor along the outer wall of the box based on a step size until the entire focus area to be detected is completely covered, and obtain all the scanned and reflected acoustic signals; Preprocess the obtained acoustic signals, and calculate the time delay difference of the ultrasonic signals of each element in each scanned area by performing beamforming on the preprocessed acoustic signals; Construct an objective function based on the spatial geometric relationship between the element coordinates of the ultrasonic phased array sensor and the focus area and the time delay difference, and perform hotspot positioning through particle swarm optimization to determine the minimum value of the objective function value, and perform hotspot coordinate positioning of the power equipment.

2. The method for hot spot positioning of the ultrasonic phased array of the power equipment according to claim 1, wherein The objective function is: ， where, ( x i ，y i ，z i ) represents the coordinates of the i -th array element; ( x, y, z ) represents the coordinates of the hot spot position to be located; v represents the propagation speed of ultrasonic waves in the medium; τ ij represents the array element i and the array element j time delay difference.

3. The method for hot spot location of the ultrasonic phased array of power equipment according to claim 1, characterized in that, The process of performing hotspot positioning through particle swarm optimization to determine the minimum value of the objective function value is specifically as follows: Initialize the particle swarm and set the maximum number of iterations; randomly generate candidate coordinates representing hotspots ( x, y, z ); Calculate the objective function value corresponding to the candidate coordinates according to the objective function; Update the particle velocity and position to make it move towards the area with a smaller objective function value; If the number of iterations reaches the maximum number of iterations or the objective function value approaches 0, determine the convergence coordinate value of the particle swarm, which is the hotspot coordinate located in this scanned area.

4. The method for hot spot localization of the ultrasonic phased array of power equipment according to claim 3, wherein The hotspot coordinate positioning of the power equipment also includes summarizing the hotspot coordinates obtained by positioning different scanned areas and correcting each hotspot coordinate using weighted average to obtain the final hotspot position.

5. The method for hot spot location of an ultrasonic phased array of a power equipment according to claim 1, wherein The preprocessing of the obtained acoustic signals includes performing empirical mode decomposition on the acoustic signals and screening the IMF components with high correlation with the original signal.

6. The method for hot spot location of ultrasonic phased array of power equipment according to claim 2, characterized in that It also includes performing Fourier transform on the denoised signal to extract features, and the extracted features include time difference of arrival, amplitude peak, and main frequency offset.

7. The method for hot spot localization of ultrasonic phased array of power equipment according to claim 1, wherein For the beamforming of the preprocessed acoustic signals, the acoustic signals of each element are weighted and superimposed to enhance the target direction signal as: ， Among them, y(t) 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 ) represents the i reflected ultrasonic signal acquired by the i th array element.

8. The method for hot spot location of ultrasonic phased array of power equipment according to claim 1, characterized in that The method of translating and scanning the ultrasonic phased array sensor along the outer wall of the box based on a step size is specifically as follows: Divide the outer wall of the box where the ultrasonic phased array sensor is set, and set nodes along the x - direction and y - direction according to the preset step size; Draw parallel lines to the y - axis for the nodes in the x - direction and parallel lines to the x - axis for the nodes in the y - direction for division, and divide the outer wall of the box into several scanned areas; Move the ultrasonic phased array sensor to each scanned area for scanning, and obtain the reflected acoustic signals received by each element in each scanned area of the outer wall of the box; Set the ultrasonic phased array sensor on the other outer walls of the power equipment, and repeat the above operations until all the outer walls are scanned completely, and end the scanning.

9. The method for hot spot location of ultrasonic phased array of power equipment according to claim 1, characterized in that The power equipment includes transformers, generators, and oil - immersed reactors.

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