Method and apparatus for assessing the severity of discharge in insulator strings based on ultraviolet colorimetry

Abstract

This invention discloses a method and apparatus for assessing the severity of discharge in insulator strings based on ultraviolet chromaticity, belonging to the field of insulator detection technology. The core of this method lies in acquiring ultraviolet images of the insulator string, preprocessing them, calculating the mean chromaticity matrix of multiple frames, and then generating a chromaticity difference matrix and its non-zero boundary index matrix. By analyzing the characteristics of the index matrix, such as the proportion of non-zero row vectors, the coefficient of variation of column vectors, and the distance change rate, the severity level of the discharge in the insulator string can be determined and its development trend predicted. This invention also provides an ultraviolet imaging apparatus for implementing this method, including a short-pass optical lens, a variable-focus imaging module, an environmental sensing unit, an image processing unit, and a digital display unit. This method can effectively identify early discharges, has high assessment accuracy, and is less affected by environmental interference.

Description

Technical Field

[0001] This invention belongs to the field of insulator detection technology, and relates to a method and device for assessing the severity of discharge in insulator strings based on ultraviolet colorimetry. Background Technology

[0002] With the advancement of new power systems, high-voltage long-distance power transmission is gradually becoming the mainstream. Insulators, as a crucial component of power system transmission and transformation equipment, directly determine the safety and stability of the power grid. Studies have shown that factors such as aging insulation materials, burrs on line fittings, and external forces such as lightning strikes and wind deflection can easily cause abnormal discharges in transmission line insulator strings.

[0003] The discharge development process of line insulator strings can be divided into three stages. In the initial discharge stage, the discharge energy is low, and only a weak corona is generated in a local area on the surface of the insulator. In the discharge development stage, the local arc extends along the surface of the insulator, forming a discontinuous short channel. In the later stage of discharge development, the arc channel forms a long-distance, large-scale disordered drifting arc.

[0004] As an emerging method for discharge detection, optical detection methods have advantages such as strong intrinsic properties and high confidence. When conducting discharge ultraviolet optical detection in a dark environment, they can be free from interference from natural light noise.

[0005] Currently, the main methods used in engineering to monitor the operating status of line insulator strings are infrared zero-measurement or drone inspection. However, infrared zero-measurement is difficult to identify slight overheating, and it is difficult to identify early discharge through drone-transmitted images. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing insulator detection technologies and provide a method and device for assessing the severity of insulator string discharge based on ultraviolet chromaticity. Specifically, it aims to solve problems such as the insensitivity of existing infrared null measurement technology to slight overheating and the difficulty of identifying early discharges during drone inspections. This invention analyzes the color characteristics (chromaticity) of the ultraviolet optical signals generated by the discharge to achieve accurate and quantitative assessment of the severity and development trend prediction of the entire process of insulator string discharge, from local corona to arcing, thereby providing an earlier and more reliable early warning method for power grid safe operation and maintenance.

[0007] This invention is achieved through the following technical solution: A method for assessing the severity of discharge in insulator strings based on ultraviolet colorimetry, comprising the following steps:

[0008] S100: Acquire ultraviolet images of the insulator string under the same field of view and perform image preprocessing. The ultraviolet images are stored in the form of a pixel matrix, and each pixel matrix unit contains pixel intensity and pixel tone information.

[0009] S200: Calculate the mean chromaticity matrix of multiple frames of ultraviolet images based on the pixel intensity matrix and pixel hue matrix of the ultraviolet images;

[0010] S300: Calculate the chromaticity difference matrix of the ultraviolet image based on the mean chromaticity matrix;

[0011] S400: Calculate the index matrix of the non-zero boundaries of the chromaticity difference matrix based on the chromaticity difference matrix;

[0012] S500: Based on the characteristics of the index matrix of the ultraviolet image, determine the severity level of discharge of the insulator string and obtain the development trend.

[0013] In step S100, the image preprocessing includes noise reduction and abnormal image recognition. The noise reduction uses a two-dimensional Gaussian filter of a specific size to perform convolution calculation on the acquired ultraviolet image. The abnormal image is determined by the maximum pixel intensity of the ultraviolet image, and different weight coefficients are assigned to the ultraviolet image according to the pixel intensity to calculate the mean chromaticity matrix. If the maximum pixel intensity is higher than the pixel intensity threshold of the image sensor, the weight coefficient of the ultraviolet image frame is assigned to 0.1. If the maximum pixel intensity is not higher than 255, the weight coefficient of the ultraviolet image frame is assigned to 1.

[0014] In step S500, the features of the index matrix of the ultraviolet image include the proportion of non-zero row vectors, the coefficient of variation of column vectors, and the rate of change of distance; the coefficient of variation of column vectors is used to measure the dispersion of the column vectors of the index matrix; the rate of change of distance is calculated based on the norm of the index matrix of the target frame and is used to characterize the rate of change of the index matrix in multiple frame intervals.

[0015] In step S500, the determination of the severity level of insulator string discharge includes the following steps:

[0016] S501: If the proportion of non-zero row vectors in the index matrix is ​​lower than the first threshold, it is determined to be a mild discharge;

[0017] S502: If the proportion of non-zero row vectors in the index matrix is ​​higher than the first threshold and the coefficient of variation of column vectors is lower than the second threshold, then it is determined to be a moderate level of discharge.

[0018] S503: If the proportion of non-zero row vectors in the index matrix is ​​higher than the third threshold and there are column vectors with a coefficient of variation higher than the second threshold, then it is determined to be a severe discharge.

[0019] In step S500, obtaining the development trend includes the following steps:

[0020] S504: Within a multi-frame interval, if the proportion of non-zero row vectors in the index matrix of the starting frame is lower than that of the last frame and the average value of the distance change rate of the index matrix is ​​higher than the fourth threshold, then it is determined that the discharge is aggravated.

[0021] S505: If the average rate of change of distance in the index matrix is ​​lower than the fifth threshold within a multi-frame interval, the discharge is determined to be stable.

[0022] S506: Within a multi-frame interval, if the proportion of non-zero row vectors in the index matrix of the starting frame is higher than that of the last frame and the average value of the distance change rate of the index matrix is ​​higher than the fourth threshold, then it is determined that the discharge is weakened.

[0023] An ultraviolet imaging device for implementing a method for assessing the severity of insulator string discharge based on ultraviolet chromaticity information, comprising:

[0024] Short-pass optical lens, used to filter out visible light noise;

[0025] A variable-focus imaging module, connected to the short-pass optical lens, is used to acquire images of the detection field of view and to match the longitudinal field of view range with the length of the insulator string;

[0026] An environmental sensing unit is used to collect environmental humidity information;

[0027] An image processing unit, connected to the variable-focus imaging module and the environmental perception unit, is used to receive image data and execute an insulator string discharge severity assessment method based on ultraviolet chromaticity information.

[0028] The digital display unit, connected to the image processing unit, is used to visualize the processing results and display the assessment conclusion of the severity of insulator string discharge.

[0029] Further preferably, the short-wavelength optical lens has a transmission band covering the solar-blind ultraviolet band, the mid-wave ultraviolet band, and the long-wave ultraviolet band, and has a peak transmittance of not less than a set threshold; the configuration of the variable-focus imaging module makes its longitudinal field of view equal to the length of the insulator string, and the angle between the lens normal and the ground does not exceed a specific angle when it is working.

[0030] Further preferably, the environmental humidity information collected by the environmental sensing unit is used to dynamically adjust the standard deviation of the two-dimensional Gaussian filter in the image preprocessing step. Specifically, when the relative humidity is higher than a set threshold, the standard deviation increases linearly with the humidity.

[0031] The present invention also provides a non-volatile computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the insulator string discharge severity assessment method based on ultraviolet colorimetric information.

[0032] This invention expands the analysis dimension from single photon intensity to chromaticity, which includes hue information, making it more sensitive to minute changes in the discharge region. By analyzing the chromaticity matrix and its boundary features, it can effectively capture weak corona discharges in local areas such as the triple junction points on the insulator surface, enabling early detection and warning of abnormal insulator discharges and buying valuable time for preventative maintenance.

[0033] This invention innovatively proposes a multi-dimensional quantitative evaluation system based on the proportion of non-zero row vectors, the coefficient of variation of column vectors, and the rate of change of distance. These characteristic parameters accurately characterize the severity of discharge from three aspects: the spatial distribution range of the discharge, the stability of the boundary morphology, and the dynamic evolution over time. This makes the evaluation process reliable, and the judgment results more scientific, objective, and accurate, effectively avoiding misjudgments or omissions caused by individual differences.

[0034] The invention can not only assess the static severity level of the current discharge, but also quantitatively predict the development trend of discharge activity (intensification, stabilization, or reduction) by calculating the distance change rate of the index matrix over consecutive frames. Attached Figure Description

[0035] Figure 1 The flowchart shows the method for assessing the severity of discharge in insulator strings based on ultraviolet colorimetry provided by this invention.

[0036] Figure 2 This is a schematic diagram of the principle structure of the ultraviolet imaging device provided by the present invention. Detailed Implementation

[0037] Example 1

[0038] like Figure 1 As shown in one embodiment, the complete workflow of the present invention is illustrated by taking the practical application of the insulator string discharge severity assessment method based on ultraviolet colorimetry in nighttime insulator string discharge detection.

[0039] S100: Acquire ultraviolet images of insulator strings under the same field of view and perform image preprocessing. The ultraviolet images are stored in the form of a pixel matrix, and each pixel matrix unit contains pixel intensity and pixel tone information.

[0040] The frame rate is no less than 1000 frames per second.

[0041] S200: Calculate the mean chromaticity matrix of multiple frames of ultraviolet images based on the pixel intensity matrix and pixel hue matrix. The specific relationship formula is as follows:

[0042] ;

[0043] in, Let be the pixel intensity matrix of the k-th frame of the ultraviolet image. Let k be the pixel tone matrix of the ultraviolet image in frame k. The number of frames in the ultraviolet image. represents the weighting coefficient of the k-th frame of the ultraviolet image.

[0044] S300: Calculate the chromaticity difference matrix S of the ultraviolet image based on the mean chromaticity matrix. (1) The specific relationship formula is as follows:

[0045] ;

[0046] ;

[0047] in, Chromaticity difference matrix No. Line 1 The element values ​​of the column, Mean chromaticity matrix No. Line 1 The element values ​​of the column, Mean chromaticity matrix The maximum element value, Mean chromaticity matrix No. Line 1 The normalized element values ​​of the column. For the row index of the ultraviolet image, This is the column index for the ultraviolet image, where M is the horizontal resolution of the ultraviolet imaging device and N is the vertical resolution of the ultraviolet imaging device.

[0048] S400: Based on the chromaticity difference matrix, calculate the index matrix R of the non-zero boundaries of the chromaticity difference matrix. The specific formula is as follows:

[0049] ;

[0050] In the formula, Let be the chromaticity difference sign matrix, and sign be the sign function.

[0051] ;

[0052] In the formula, The first chromaticity difference sign matrix row vectors. This indicates finding the row vector. The set of indices of all elements whose median is the maximum value (i.e., 1). This indicates finding the row vector. The median is the set of indices of all elements whose median is the minimum (i.e., -1). `min` is a function that returns the minimum value, and `max` is a function that returns the maximum value. For the index matrix R, the first... Row vectors.

[0053] S500: Based on the characteristics of the index matrix of the ultraviolet image, determine the severity level of discharge of the insulator string and obtain the development trend.

[0054] In step S100, the image preprocessing includes noise reduction and abnormal image recognition. Noise reduction uses a two-dimensional Gaussian filter to perform convolution calculations on the acquired ultraviolet image; the Gaussian kernel size of the two-dimensional Gaussian filter is 3×3. Abnormal images are determined by the maximum pixel intensity of the ultraviolet image. If the maximum pixel intensity is higher than the image sensor's pixel intensity threshold, a weight coefficient of 0.1 is assigned to that frame. This weight coefficient is used in step S200 to calculate the mean chromaticity matrix of multiple frames of ultraviolet images. .

[0055] In Gaussian filtering calculations, considering the potential scattering interference of water molecules on the discharge light signal in high-humidity environments, it is necessary to improve the signal-to-noise ratio of the ultraviolet image, i.e., increase the Gaussian kernel standard deviation and enhance the filtering strength. Therefore, in this embodiment, a formula showing the positive correlation between the Gaussian kernel standard deviation σ and the relative humidity h is introduced.

[0056] If the relative humidity is less than 80%, the Gaussian kernel standard deviation is 0.8. If the relative humidity is greater than 80%, the specific formula for the relationship between the Gaussian kernel standard deviation and the relative humidity is as follows:

[0057]

[0058] In the formula, σ is the Gaussian kernel standard deviation, and h is the relative humidity.

[0059] The image sensor is 8-bit. If the maximum pixel intensity is higher than 255, the weight coefficient of the frame is 0.1; if the maximum pixel intensity is not higher than 255, the weight coefficient of the frame is 1.

[0060] In step S500, the features of the index matrix of the ultraviolet image include the proportion of non-zero row vectors, the coefficient of variation of column vectors, and the rate of change of distance.

[0061] The formula for calculating the coefficient of variation of the column vectors of the index matrix is:

[0062] ;

[0063] In the formula, Let be the coefficient of variation of the j-th column vector of the index matrix. It is the element in the i-th row and j-th column of the index matrix.

[0064] The formula for calculating the distance change rate D of the index matrix is:

[0065] ;

[0066] In the formula, t is the time index. Let be the index matrix of the t-th frame. Let be the index matrix of the (t+1)th frame. Let f(t) be the Frobenius norm of the index matrix of frame t. Let T be the Frobenius norm of the difference between the index matrices of frame t+1 and frame t, where T is the number of time intervals, i.e., the number of frames.

[0067] In step S500, the determination of the severity level of insulator string discharge includes the following steps:

[0068] S501: If the proportion of non-zero row vectors in the index matrix is ​​less than 20%, a discharge occurs in the local area of ​​the three junction points on the surface of the corresponding insulator string, which is judged as a mild discharge.

[0069] S502: If the proportion of non-zero row vectors in the index matrix is ​​higher than 20% and the coefficient of variation of column vectors is lower than 15%, a discharge occurs on the surface of the corresponding insulator string, which is judged as a moderate level of discharge.

[0070] S503: If the proportion of non-zero row vectors in the index matrix is ​​higher than 40% and there is a column vector with a coefficient of variation higher than 15%, an arc is formed at both ends of the corresponding insulator string, which is judged as severe discharge.

[0071] In step S500, obtaining the development trend includes the following steps:

[0072] S504: Calculate the distance change rate of the index matrix in a multi-frame interval. If the proportion of non-zero row vectors in the index matrix of the starting frame is lower than that of the non-zero row vectors in the index matrix of the last frame and the average distance change rate of the index matrix is ​​higher than 20%, the discharge of the insulator string is aggravated.

[0073] S505: Calculate the distance change rate of the index matrix in multiple frame intervals. If the average distance change rate of the index matrix is ​​less than 10%, the discharge of the corresponding insulator string is stable.

[0074] S506: Calculate the distance change rate of the index matrix in a multi-frame interval. If the proportion of non-zero row vectors in the index matrix of the starting frame is higher than that of the non-zero row vectors in the index matrix of the last frame and the average distance change rate of the index matrix is ​​higher than 20%, the discharge of the corresponding insulator string is weakened.

[0075] Example 2

[0076] like Figure 2 As shown, an ultraviolet imaging device for assessing the severity of insulator string discharge based on ultraviolet chromaticity information includes,

[0077] The short-pass optical lens filters out visible light noise; its transmission bands are solar-blind ultraviolet (200-280nm), mid-wave ultraviolet (280-315nm), and long-wave ultraviolet (315-400nm), with a peak transmittance of not less than 30%.

[0078] A variable-focus imaging module is connected to a short-pass optical lens to acquire images of the detection field of view, making the longitudinal field of view equal to the length of the insulator string; the camera elevation angle is no higher than 45°; the elevation angle is the angle between the normal of the short-pass optical lens and the ground;

[0079] An environmental sensing unit collects ambient humidity and adjusts the standard deviation of the Gaussian kernel. The ambient humidity information collected by the environmental sensing unit is used to dynamically adjust the standard deviation of the two-dimensional Gaussian filter in the image preprocessing step. Specifically, when the relative humidity is higher than a set threshold, the standard deviation increases linearly with the humidity.

[0080] The image processing unit, which is connected to the zoom imaging module and the environment sensing unit, receives discharge photons and calculates chromaticity information, and executes an insulator string discharge severity assessment method based on ultraviolet chromaticity information.

[0081] The digital display unit, connected to the image processing unit, visualizes the mean chromaticity matrix on the ultraviolet image and displays the assessment results of the insulator string discharge severity.

[0082] The power supply unit provides the operating power for the ultraviolet imaging device.

[0083] Example 3

[0084] This embodiment provides a non-volatile computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the insulator string discharge severity assessment method based on ultraviolet colorimetric information described in Embodiment 1.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating severity of discharge of an insulator string based on ultraviolet chromaticity, characterized by, The method comprises the following steps: S100: acquiring an ultraviolet image of the insulator string under the same field of view condition and performing image preprocessing, wherein the ultraviolet image is stored in the form of a pixel matrix, and each pixel matrix unit contains pixel intensity and pixel tone information; S200: calculating a mean chroma matrix of the multiple frames of ultraviolet images based on the pixel intensity matrix and the pixel tone matrix of the multiple frames of ultraviolet images; S300: calculating a chroma difference matrix of the ultraviolet image according to the mean chroma matrix; S400: calculating an index matrix of the non-zero boundary of the chroma difference matrix according to the chroma difference matrix; S500: determining the severity level of the insulator string discharge and obtaining the development trend according to the characteristics of the index matrix of the ultraviolet image, wherein the characteristics of the index matrix of the ultraviolet image include the proportion of non-zero row vectors, the column vector coefficient of variation, and the distance change rate; The column vector coefficient of variation is used to measure the discrete degree of the column vector of the index matrix; The distance change rate is calculated based on the norm of the target frame index matrix and is used to represent the change rate of the index matrix in the multiple frame interval; The severity level determination of the insulator string discharge comprises: S501: if the proportion of non-zero row vectors of the index matrix is lower than a first threshold value, the insulator string discharge is determined to be mild; S502: if the proportion of non-zero row vectors of the index matrix is higher than the first threshold value and the column vector coefficient of variation is lower than a second threshold value, the insulator string discharge is determined to be moderate; S503: if the proportion of non-zero row vectors of the index matrix is higher than a third threshold value and there is a column vector coefficient of variation higher than the second threshold value, the insulator string discharge is determined to be severe; The development trend obtaining comprises: S504: in the multiple frame interval, if the proportion of non-zero row vectors of the index matrix of the starting frame is lower than that of the end frame and the average value of the distance change rate of the index matrix is higher than a fourth threshold value, the insulator string discharge is determined to be aggravated; S505: in the multiple frame interval, if the average value of the distance change rate of the index matrix is lower than a fifth threshold value, the insulator string discharge is determined to be stable; S506: in the multiple frame interval, if the proportion of non-zero row vectors of the index matrix of the starting frame is higher than that of the end frame and the average value of the distance change rate of the index matrix is higher than the fourth threshold value, the insulator string discharge is determined to be weakened.

2. The method of claim 1, wherein, In step S100, the image preprocessing comprises noise reduction and abnormal image recognition; the noise reduction adopts a two-dimensional Gaussian filter to perform convolution calculation on the acquired ultraviolet image; the abnormal image is determined by the maximum value of the pixel intensity of the ultraviolet image, and different weight coefficients are given to the ultraviolet image according to the pixel intensity, which is used to calculate the mean chroma matrix.

3. An ultraviolet imaging apparatus for carrying out the method of claim 1 or 2, characterized by It comprises: a short-wave-pass optical lens for filtering visible light noise; a variable-focus imaging module connected with the short-wave-pass optical lens, used for acquiring images of the detection field of view and matching the longitudinal field of view range with the length of the insulator string; an environment sensing unit for acquiring environmental humidity information; an image processing unit connected with the variable-focus imaging module and the environment sensing unit, used for receiving image data and performing the method of claim 1 or 2; a digital display unit connected with the image processing unit, used for visualizing the processing result and displaying the evaluation conclusion of the severity of the insulator string discharge.

4. The ultraviolet imaging device of claim 3, wherein, The transmission wave band of the short-wave optical lens covers the solar-blind ultraviolet wave band, the middle-wave ultraviolet wave band and the long-wave ultraviolet wave band, and has a peak transmittance not lower than a set threshold; the configuration of the variable-focus imaging module is such that the longitudinal field of view range thereof is equal to the length of the insulator string, and the angle between the lens normal and the ground during operation is not more than a specific angle.

5. The ultraviolet imaging device of claim 3, wherein, The environmental humidity information collected by the environment perception unit is used to dynamically adjust the standard deviation of the two-dimensional Gaussian filter in the image preprocessing step, specifically, when the relative humidity is higher than a set threshold, the standard deviation increases linearly with the humidity.

6. A non-transitory computer readable storage medium storing a computer program, characterized in that, The computer program, when executed by a processor, implements the steps of the method of claim 1 or 2.

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