CN119224502B - Nondestructive testing equipment and nondestructive testing method for insulation performance of locomotive converter - Google Patents
Nondestructive testing equipment and nondestructive testing method for insulation performance of locomotive converter Download PDFInfo
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- 238000009413 insulation Methods 0.000 title claims abstract description 84
- 230000003137 locomotive effect Effects 0.000 title claims abstract description 75
- 238000000034 method Methods 0.000 title claims abstract description 49
- 238000009659 non-destructive testing Methods 0.000 title claims abstract description 19
- 238000001514 detection method Methods 0.000 claims abstract description 41
- 238000012545 processing Methods 0.000 claims abstract description 30
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- 230000015556 catabolic process Effects 0.000 claims description 26
- 230000000630 rising effect Effects 0.000 claims description 23
- 230000011218 segmentation Effects 0.000 claims description 19
- 230000000877 morphologic effect Effects 0.000 claims description 15
- 238000004458 analytical method Methods 0.000 claims description 14
- 238000010219 correlation analysis Methods 0.000 claims description 13
- 238000007781 pre-processing Methods 0.000 claims description 8
- 241001270131 Agaricus moelleri Species 0.000 claims description 7
- 230000007797 corrosion Effects 0.000 claims description 6
- 238000005260 corrosion Methods 0.000 claims description 6
- 238000004891 communication Methods 0.000 claims description 4
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- 238000012360 testing method Methods 0.000 abstract description 6
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
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- G06T7/10—Segmentation; Edge detection
- G06T7/136—Segmentation; Edge detection involving thresholding
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- G—PHYSICS
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/10—Segmentation; Edge detection
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
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Abstract
The invention discloses a nondestructive testing device and method for insulation performance of a locomotive converter, which relate to the technical field of performance testing of electrical equipment, and aim to solve the technical problems that signals obtained by nondestructive testing of the insulation performance of the locomotive converter at present contain a large number of higher harmonics, the attenuation of the signals is faster, and the insulation state of the converter cannot be monitored in real time, and comprise a testing device, an image extraction unit, an image conversion unit, an image processing unit, an image storage unit, a data analysis processing unit and a testing result output unit, the invention adopts non-contact detection, does not need power-off, corona and pressure in the detection process, can perform insulation performance nondestructive detection in the normal operation process of the locomotive converter, does not influence the normal operation of the locomotive, is convenient for finding out possible problems of an insulation system in time, avoids secondary faults caused by insulation faults, and ensures the safety and reliability of the operation of the locomotive.
Description
Technical Field
The invention relates to the technical field of performance detection of electrical equipment, in particular to nondestructive detection equipment and method for insulation performance of a locomotive converter.
Background
Currently, for equipment such as locomotive converters, insulation systems are the most basic of the complex systems of locomotive converters and are also susceptible to failure and structural damage from various electrical, thermal, mechanical stresses and electromagnetic effects. As locomotive converters move toward higher power densities, higher integration, and miniaturization, the structure and design of the insulation system has become more complex. In the normal operation process of the locomotive converter, alternating voltage and current, mechanical vibration and thermal stress can enable the insulation system to generate partial discharge, and excessive partial discharge is not only an electromagnetic interference source, but also can enable the insulation system of the converter to generate phenomena of deformation, crack, breakdown and the like, so that more serious faults are caused, and further more complex secondary faults are caused.
Therefore, to ensure proper operation of the locomotive converter insulation system during long service periods, it is necessary to monitor the status of the locomotive converter insulation system in real time.
At present, the most commonly used insulation performance test method is to test the insulation performance such as partial discharge, dielectric loss tangent, absorption ratio, polarization index and the like when the locomotive converter works, however, the test methods are in a power-off state and require an external power supply, and in order to ensure the test accuracy, a great amount of preparation work is required to be done besides equipment replacement when the measurement is carried out, and the requirement on the mastering of test time is higher;
The partial discharge is a discharge process caused by breakdown of a partial region in an insulating medium, can be regarded as a set of a plurality of partial discharge sources, is usually pulsed and is usually received by an ultrahigh frequency sensor, and the partial discharge detection method can be used for monitoring the frequency domain characteristic of the partial discharge and the time domain characteristic of the partial discharge, so that the obtained data is comprehensive.
Most partial discharge detection methods in the prior art can detect the whole discharge signal by using an ultrahigh frequency sensor and then analyze data, but from the measurement principle of the ultrahigh frequency sensor, the detected signal contains a large amount of higher harmonics, and in the initial stage of discharge, the signal attenuation monitored by the ultrahigh frequency sensor is relatively fast, and the insulation state of the converter cannot be monitored in real time.
Disclosure of Invention
The invention aims to provide nondestructive testing equipment and method for insulation performance of a locomotive converter, which are used for solving the technical problems that signals obtained by nondestructive testing of the insulation performance of the current locomotive converter contain a large number of higher harmonics, the attenuation of the signals is rapid, and the insulation state of the converter cannot be monitored in real time.
In order to solve the technical problems, the invention provides the technical scheme that the nondestructive testing equipment for the insulation performance of the locomotive converter comprises the following components:
the detection device is used for applying partial discharge signals with preset intensity to the locomotive converter and receiving the partial discharge signals fed back by the locomotive converter, and comprises an electric signal generating device and a partial discharge detection device, wherein the electric signal generating device is used for generating the partial discharge signals, and the partial discharge detection device is used for receiving feedback signals;
the image extraction unit is connected with the detection device and is used for carrying out Fourier transform on the partial discharge signal and converting the partial discharge signal into a partial discharge image;
the image conversion unit is connected with the image extraction unit and is used for converting the partial discharge image into a partial discharge gray scale image and further converting the partial discharge gray scale image into a partial discharge halftone image;
the image processing unit is connected with the image conversion unit and is used for carrying out gray segmentation and filtering processing on the partial discharge gray images;
an image storage unit connected to the image processing unit for storing the partial discharge gray-scale image and the partial discharge halftone image, respectively;
the data analysis unit is connected with the image processing unit and is used for preprocessing the partial discharge halftone image so as to judge the insulation condition of the locomotive converter;
The data analysis processing unit is connected with the data analysis unit and is used for carrying out correlation analysis on the partial discharge gray level image and the partial discharge halftone image to obtain an analysis result;
the detection result output unit is connected with the data analysis processing unit and is used for displaying, storing and analyzing the analysis result and outputting the final detection result of the nondestructive detection of the insulation performance of the locomotive converter in an image form.
According to the invention, through the arrangement of the electric signal generating device and the partial discharge detecting device, a non-contact detecting method is adopted, power failure, corona and pressure are not needed in the detecting process, the insulation performance of the locomotive converter can be subjected to high-efficiency and accurate nondestructive detection in the normal running process of the locomotive converter, the possible problems of an insulation system can be found in time under the condition that the normal running of the locomotive is not influenced, the secondary faults caused by insulation faults are avoided, and the running safety and reliability of the locomotive are ensured.
Preferably, the conversion of the partial discharge halftone image is a gradation process by the following formula:
;
In the formula, For a partial discharge gray scale image pixel,For a partial discharge halftone image pixel,The number of columns and the number of rows of the partial discharge gray scale image pixel points are respectively.
Preferably, the image processing unit performs gray scale division of the partial discharge gray scale image including:
performing first binarization segmentation on partial discharge gray scale image by Positioning pixel points with the discharge times exceeding the preset times in the partial discharge gray level image;
In the formula, For partial discharge grey scale imageThe gray value at which the color is to be changed,In order to set the threshold value in advance,Is a binarized image;
performing second binarization division on the partial discharge gray scale image of the first binarization division to locate rising edges and falling edges of each discharge pulse and obtain rising edge coordinate data of each pulse 、Falling edge coordinate data、And drawing rising edge or falling edge curves of the pulses, wherein the judgment of the rising edge and the falling edge can be determined through slope change;
Dividing the partial discharge gray scale image divided by the second binarization for the third time to determine half-peak time of the partial discharge pulse Half-peak time data is obtained by calculating the time point when the gray values at the two sides of the pulse peak value are reduced to half.
Preferably, the rising edge and falling edge coordinate data of the partial discharge pulse detected by the second binarization division are respectively recorded as A pointPoint BConnecting the points A and B to obtain a ray, and recording the equation of the ray as;
In the formula,,。
Preferably, the gray level of the partial discharge gray level image after the second binarization segmentation is set asCounting gray values of all pixel points between the point A and the point B of each discharge pulse, normalizing the counting result, and normalizing the pixel points into the gray valuesThe value of the interval and the gray level corresponding to the pixel point are recorded asThe formula is;
In the formula,Is the gray level corresponding to the pixel point,For any pixel of a partial discharge greyscale imageIs a gray value of (a).
Preferably, the filtering processing of the partial discharge gray scale image by the image processing unit includes:
performing median filtering and mean filtering on the partial discharge gray level image subjected to the second binarization segmentation to obtain a filtered image;
The median filtering formula is In which, in the process,For the pixel values of the original image,For the filtered image pixel values,Is a filter window;
The mean value filtering formula is In which, in the process,In order to filter the window size,,;
Obtaining local gray average value of filtered imageIn which, in the process,For filtered imageThe gray value at which the color is to be changed,Is the image size;
According to the formula Calculating local gray mean square valuePerforming enhancement processing on the image;
Calculating the difference between half-peak time data of two adjacent discharge pulses To obtain the rising edge speed of the discharge pulseIn which, in the process,Is the difference in rising edge height of adjacent pulses.
Preferably, the data analysis processing unit performs correlation analysis on the partial discharge gray scale image and the partial discharge halftone image, and the obtaining the analysis result includes:
setting a certain pixel point of the partial discharge halftone image, marking as a D point, searching gray scales corresponding to the abscissa of two discharge pulses adjacent to the D point, and marking as first gray scales respectively And a second gray scaleIf (if)D is located on the first discharge pulse ifD point is located on the second discharge pulse ifDetermining the discharge pulse corresponding to the abscissa where the point D is positioned as the pulse to be analyzed according to the rising edge speeds of the discharge pulses at the two sides of the point D of the first discharge pulse;
if the D point is located on the first discharge pulse, searching the gray level corresponding to the abscissa of the discharge pulse nearest to the D point, and marking as the third gray level If the vertical straight line extension line where the point D is located has an intersection point with the third pulse curve, and the gray level corresponding to the intersection pointThe D point is located on the first discharge pulse, otherwise the D point is located on the second discharge pulse.
Preferably, the data analysis unit pre-processes the partial discharge halftone image includes:
The partial discharge halftone image is processed by an OTSU threshold segmentation method to obtain a binary image, and the OTSU algorithm calculates the inter-class variance To determine a threshold valueSo thatThe maximum, in the formula,、Is the duty ratio of two types of pixel points,、The average value of two types of pixel points;
Median filtering is carried out on the obtained binary image, pixel information of the image is reserved, morphological expansion operation is carried out on the image after the median filtering, and the image is expanded, so that the area of an insulation failure area is obtained The expansion operation formula isIn which, in the process,As the original image is to be taken,Is a structural element;
Performing color reversal treatment on the partial discharge halftone image subjected to the first binarization segmentation to obtain a color reversal image, wherein the color reversal formula is as follows ;
In the formula,For the pixel values of the original image,Is the pixel value of the image after the color reversal;
Positioning pixel positions of areas where the discharge pulse D points are located in the inverse color images, respectively marking and deleting the positioned pixel positions to obtain residual inverse color images, performing median filtering on the residual inverse color images to obtain filtered inverse color images, performing morphological filling operation on the filtered inverse color images to obtain filled inverse color images, and filling the holes by scanning the images.
Preferably, the data analysis unit pre-processes the partial discharge halftone image further includes:
Morphological corrosion operation is carried out on the filled anti-color image to obtain a corroded anti-color image, wherein the corrosion formula is that Performing the color reversal treatment on the corroded color reversal image to obtain a color reversal treated image;
Morphological closing operation is carried out on the image after the color reversing treatment to obtain an insulation breakdown spot image, wherein the closing operation is to expand and then corrode, and median filtering is carried out on the insulation breakdown spot image to obtain a filtered insulation breakdown spot image;
Morphological filling operation is carried out on the filtered dielectric breakdown speckle image, and a communication area with the largest pixel point is obtained and is recorded as ,The number of the pixel points is recorded as the number of the pixelsThenThe pixel number of the region is the pixel number of the breakdown spot regionPixel count of area breakdown spot area,In which, in the process,Then;
According to the formulaCalculating the insulation breakdown rateWhen (when)If the voltage is larger than the preset breakdown threshold, judging that the insulation of the locomotive converter fails, wherein,Is the area of the insulating surface of the locomotive converter.
A nondestructive testing method for insulation performance of a locomotive converter comprises the following steps:
S1, applying partial discharge signals with preset intensity to a locomotive converter by using a detection device, exciting by applying discharge voltages to a high-voltage side and a low-voltage side, generating partial discharge signals in a discharge excitation area, and monitoring the partial discharge signals;
s2, carrying out Fourier transform on partial discharge signals fed back by the locomotive converter, and converting the partial discharge signals into partial discharge images;
S3, converting the partial discharge image into a partial discharge gray scale image, and further converting the partial discharge gray scale image into a partial discharge halftone image;
S4, preprocessing the partial discharge gray level image and the partial discharge halftone image;
S5, carrying out correlation analysis on the partial discharge gray level image and the partial discharge halftone image to obtain an analysis result, wherein in the correlation analysis, a correlation coefficient between the partial discharge gray level image and the partial discharge halftone image can be calculated:
;
In the formula, For the values of the corresponding pixels of the two images,Is the average value of the pixel values of the image;
And S6, displaying, storing and analyzing the analysis result, and outputting a final detection result of nondestructive detection of the insulation performance of the locomotive converter in a form of an image, so that a user can intuitively understand the insulation performance condition of the locomotive converter.
Compared with the prior art, the invention has the beneficial effects that:
1. According to the invention, through the arrangement of the electric signal generating device and the partial discharge detecting device, a non-contact detecting method is adopted, power failure, corona and pressure are not needed in the detecting process, the insulation performance of the locomotive converter can be subjected to high-efficiency and accurate nondestructive detection in the normal running process of the locomotive converter, the possible problems of an insulation system can be found in time under the condition that the normal running of the locomotive is not influenced, the secondary faults caused by insulation faults are avoided, and the running safety and reliability of the locomotive are ensured.
2. The invention also obtains more accurate detection results by focusing key characteristics of the partial discharge pulse and carrying out correlation analysis on the partial discharge gray level image and the halftone image, can capture tiny changes of an insulation system more sensitively, is beneficial to finding potential insulation fault risks in advance, and provides powerful support for maintenance decision.
3. The invention can monitor the partial discharge source in real time, accurately determine the specific position of insulation failure, realize quick fault location, and can perform partial discharge measurement on the locomotive converter in a conventional insulation state, comprehensively cover multiple aspects of insulation performance evaluation of the locomotive converter, accurately locate the fault occurrence from the conventional detection in daily life, provide a one-stop solution for maintenance and management of an insulation system of the locomotive converter, and effectively improve the maintenance efficiency and reliability of the insulation system.
Drawings
Fig. 1 is a diagram of the apparatus of the present invention.
Detailed Description
In the first embodiment, as shown in fig. 1, the invention relates to a nondestructive testing device for insulation performance of a locomotive converter, which comprises:
the detection device is used for applying partial discharge signals with preset intensity to the locomotive converter and receiving the partial discharge signals fed back by the locomotive converter, and comprises an electric signal generating device and a partial discharge detection device, wherein the electric signal generating device is used for generating the partial discharge signals, and the partial discharge detection device is used for receiving feedback signals;
the image extraction unit is connected with the detection device and is used for carrying out Fourier transform on the partial discharge signal and converting the partial discharge signal into a partial discharge image;
the image conversion unit is connected with the image extraction unit and is used for converting the partial discharge image into a partial discharge gray scale image and further converting the partial discharge gray scale image into a partial discharge halftone image;
the image processing unit is connected with the image conversion unit and is used for carrying out gray segmentation and filtering processing on the partial discharge gray images;
an image storage unit connected to the image processing unit for storing the partial discharge gray-scale image and the partial discharge halftone image, respectively;
the data analysis unit is connected with the image processing unit and is used for preprocessing the partial discharge halftone image so as to judge the insulation condition of the locomotive converter;
The data analysis processing unit is connected with the data analysis unit and is used for carrying out correlation analysis on the partial discharge gray level image and the partial discharge halftone image to obtain an analysis result;
the detection result output unit is connected with the data analysis processing unit and is used for displaying, storing and analyzing the analysis result and outputting the final detection result of the nondestructive detection of the insulation performance of the locomotive converter in an image form.
According to the invention, through the arrangement of the electric signal generating device and the partial discharge detecting device, a non-contact detecting method is adopted, power failure, corona and pressure are not needed in the detecting process, the insulation performance of the locomotive converter can be subjected to high-efficiency and accurate nondestructive detection in the normal running process of the locomotive converter, the possible problems of an insulation system can be found in time under the condition that the normal running of the locomotive is not influenced, the secondary faults caused by insulation faults are avoided, and the running safety and reliability of the locomotive are ensured.
In a second embodiment, as shown in fig. 1, as another embodiment of the present invention, a nondestructive testing method for insulation performance of a locomotive converter includes the following steps:
S1, applying partial discharge signals with preset intensity to a locomotive converter by using a detection device, exciting by applying discharge voltages to a high-voltage side and a low-voltage side, generating partial discharge signals in a discharge excitation area, and monitoring the partial discharge signals;
s2, carrying out Fourier transform on partial discharge signals fed back by the locomotive converter, and converting the partial discharge signals into partial discharge images;
S3, converting the partial discharge image into a partial discharge gray scale image, further converting the partial discharge gray scale image into a partial discharge halftone image, wherein the partial discharge halftone image is converted by Performing hierarchical treatment;
In the formula, For a partial discharge gray scale image pixel,For a partial discharge halftone image pixel,The number of columns and the number of rows of the partial discharge gray level image pixel points are respectively;
S4, preprocessing the partial discharge gray level image and the partial discharge halftone image;
S401, preprocessing partial discharge gray scale images;
S401a, performing first binarization segmentation on the partial discharge gray scale image by Positioning pixel points with the discharge times exceeding the preset times in the partial discharge gray level image;
In the formula, For partial discharge grey scale imageThe gray value at which the color is to be changed,In order to set the threshold value in advance,Is a binarized image;
S401b, performing second binarization division on the partial discharge gray scale image of the first binarization division, locating rising edges and falling edges of each discharge pulse, and obtaining rising edge coordinate data of each pulse 、Falling edge coordinate data、And drawing rising edge or falling edge curves of the pulses, determining rising edge and falling edge by slope change, and recording the coordinate data of the rising edge and the falling edge of the partial discharge pulse detected by the second binarization segmentation as A pointPoint BConnecting the points A and B to obtain a ray, and recording the equation of the ray as;
In the formula,,;
S401c, setting the gray level of the partial discharge gray level image after the second binarization segmentation asCounting gray values of all pixel points between the point A and the point B of each discharge pulse, normalizing the counting result, and normalizing the pixel points into the gray valuesThe value of the interval and the gray level corresponding to the pixel point are recorded asThe formula is;
In the formula,Is the gray level corresponding to the pixel point,For graying any pixel of the image by partial dischargeGray values of (2);
s401d, dividing the partial discharge gray scale image of the second binarization division for the third time to determine half-peak time of the partial discharge pulse Half-peak time data is obtained by calculating the time point when the gray values at two sides of the pulse peak value are reduced to half;
S401e, performing median filtering and mean filtering on the partial discharge gray level image subjected to the second binarization segmentation to obtain a filtered image;
The median filtering formula is In which, in the process,For the pixel values of the original image,For the filtered image pixel values,Is a filter window;
The mean value filtering formula is In which, in the process,In order to filter the window size,,;
S401f, solving local gray average value of the filtered imageIn which, in the process,For filtered imageThe gray value at which the color is to be changed,Is the image size;
s401g according to the formula Calculating local gray mean square valuePerforming enhancement processing on the image;
S401h, calculating the difference value between the half-peak time data of two adjacent discharge pulses To obtain the rising edge speed of the discharge pulseIn which, in the process,The rising edge height difference of adjacent pulses;
s402, partial discharge halftone image preprocessing comprises;
S402a, processing the partial discharge halftone image by an OTSU threshold segmentation method to obtain a binary image, and calculating an inter-class variance by an OTSU algorithm To determine a threshold valueSo thatMaximum;
In the formula, 、Is the duty ratio of two types of pixel points,、The average value of two types of pixel points;
S402b, median filtering the obtained binary image, retaining pixel information of the image, performing morphological expansion operation on the image after median filtering, and expanding the image to obtain the area of the insulation failure region The expansion operation formula isIn which, in the process,As the original image is to be taken,Is a structural element;
S402c, performing inverse color treatment on the partial discharge halftone image divided by binarization for the first time to obtain an inverse color image, wherein an inverse color formula is as follows ;
In the formula,For the pixel values of the original image,Is the pixel value of the image after the color reversal;
S402D, positioning pixel positions of areas where discharge pulse D points are located in the inverse color images, respectively marking and deleting the positioned pixel positions to obtain residual inverse color images, performing median filtering on the residual inverse color images to obtain filtered inverse color images, performing morphological filling operation on the filtered inverse color images to obtain filled inverse color images, wherein the filling operation can be realized by scanning the images and filling holes;
s402e, carrying out morphological corrosion operation on the filled anti-color image to obtain a corroded anti-color image, wherein the corrosion formula is as follows Performing the color reversal treatment on the corroded color reversal image to obtain a color reversal treated image;
s402f, performing morphological closing operation on the image subjected to the color reversal treatment to obtain an insulation breakdown spot image, wherein the closing operation is to expand and then corrode, and performing median filtering on the insulation breakdown spot image to obtain a filtered insulation breakdown spot image;
S402g, performing morphological filling operation on the filtered dielectric breakdown speckle image to obtain a communication area with the largest pixel point, and marking the communication area as ,The number of the pixel points is recorded as the number of the pixelsThenThe pixel number of the region is the pixel number of the breakdown spot regionPixel count of area breakdown spot area,In which, in the process,Then;
S402h, according to the formulaCalculating the insulation breakdown rateWhen (when)If the voltage is larger than the preset breakdown threshold, judging that the insulation of the locomotive converter fails, wherein,An area that is an insulating surface of the locomotive converter;
S5, carrying out correlation analysis on the partial discharge gray level image and the partial discharge halftone image to obtain an analysis result, wherein in the correlation analysis, a correlation coefficient between the partial discharge gray level image and the partial discharge halftone image can be calculated:
;
In the formula, For the values of the corresponding pixels of the two images,Is the average value of the pixel values of the image;
S501, setting a certain pixel point of a partial discharge halftone image, marking the pixel point as a D point, searching gray scales corresponding to the abscissa of two discharge pulses adjacent to the D point, and marking the gray scales as first gray scales respectively And a second gray scaleIf (if)D is located on the first discharge pulse ifD point is located on the second discharge pulse ifDetermining the discharge pulse corresponding to the abscissa where the point D is positioned as the pulse to be analyzed according to the rising edge speeds of the discharge pulses at the two sides of the point D of the first discharge pulse;
S502, if the D point is located on the first discharge pulse, searching the gray level corresponding to the abscissa of the discharge pulse nearest to the D point, and marking as the third gray level If the vertical straight line extension line where the point D is located has an intersection point with the third pulse curve, and the gray level corresponding to the intersection pointD point is located on the first discharge pulse, otherwise D point is located on the second discharge pulse;
According to the invention, by focusing the key characteristics of the partial discharge pulse and carrying out correlation analysis on the partial discharge gray level image and the halftone image, a more accurate detection result is obtained, the tiny change of an insulation system can be captured more sensitively, the potential insulation fault risk can be found in advance, and a powerful support is provided for maintenance decision;
S6, displaying, storing and analyzing the analysis result, and outputting a final detection result of nondestructive detection of the insulation performance of the locomotive converter in a form of an image, so that a user can intuitively understand the insulation performance condition of the locomotive converter;
the invention can monitor the partial discharge source in real time, accurately determine the specific position of insulation failure, realize quick fault location, and can perform partial discharge measurement on the locomotive converter in a conventional insulation state, comprehensively cover multiple aspects of insulation performance evaluation of the locomotive converter, accurately locate the fault occurrence from the conventional detection in daily life, provide a one-stop solution for maintenance and management of an insulation system of the locomotive converter, and effectively improve the maintenance efficiency and reliability of the insulation system.
The embodiments of the present invention are disclosed as preferred embodiments, but not limited thereto, and those skilled in the art will readily appreciate from the foregoing description that various modifications and variations can be made without departing from the spirit of the present invention.
Claims (6)
1. A non-destructive testing device for insulation performance of a locomotive converter, comprising:
The detection device is used for applying partial discharge signals with preset intensity to the locomotive converter and receiving the partial discharge signals fed back by the locomotive converter;
the image extraction unit is connected with the detection device and is used for carrying out Fourier transform on the partial discharge signal and converting the partial discharge signal into a partial discharge image;
the image conversion unit is connected with the image extraction unit and is used for converting the partial discharge image into a partial discharge gray scale image and further converting the partial discharge gray scale image into a partial discharge halftone image;
the image processing unit is connected with the image conversion unit and is used for carrying out gray segmentation and filtering processing on the partial discharge gray image;
an image storage unit connected to the image processing unit for storing the partial discharge gray-scale image and the partial discharge halftone image, respectively;
the data analysis unit is connected with the image processing unit and is used for preprocessing the partial discharge halftone image so as to judge the insulation condition of the locomotive converter;
The data analysis processing unit is connected with the data analysis unit and is used for carrying out correlation analysis on the partial discharge gray level image and the partial discharge halftone image to obtain an analysis result;
the detection result output unit is connected with the data analysis processing unit and is used for displaying, storing and analyzing the analysis result and outputting the final detection result in an image form;
The gray scale division of the partial discharge gray scale image comprises the following steps:
performing first binarization segmentation on partial discharge gray scale image by Positioning the pixel points with the discharge times exceeding the preset times in the partial discharge gray level image, wherein in the formula,For partial discharge grey scale imageThe gray value at which the color is to be changed,In order to set the threshold value in advance,Is a binarized image;
performing second binarization division on the partial discharge gray scale image of the first binarization division to locate rising edges and falling edges of each discharge pulse and obtain rising edge coordinate data of each pulse 、Falling edge coordinate data、And drawing rising edge or falling edge curves of the pulses;
Dividing the partial discharge gray scale image divided by the second binarization for the third time to determine half-peak time of the partial discharge pulse Half-peak time data is obtained by calculating the time point when the gray values at two sides of the pulse peak value are reduced to half;
the partial discharge halftone image is converted by Performing a step-wise treatment, wherein,For a partial discharge gray scale image pixel,For a partial discharge halftone image pixel,The number of columns and the number of rows of the partial discharge gray level image pixel points are respectively;
Calculating the difference between half-peak time data of two adjacent discharge pulses To obtain the rising edge speed of the discharge pulseIn which, in the process,The rising edge height difference of adjacent pulses;
the data analysis processing unit performs correlation analysis on the partial discharge gray level image and the partial discharge halftone image, and the obtaining of an analysis result includes:
setting a certain pixel point of the partial discharge halftone image, marking as a D point, searching gray scales corresponding to the abscissa of two discharge pulses adjacent to the D point, and marking as first gray scales respectively And a second gray scaleIf (if)D is located on the first discharge pulse ifD point is located on the second discharge pulse ifDetermining the discharge pulse corresponding to the abscissa where the point D is positioned as the pulse to be analyzed according to the rising edge speeds of the discharge pulses at the two sides of the point D of the first discharge pulse;
if the D point is located on the first discharge pulse, searching the gray level corresponding to the abscissa of the discharge pulse nearest to the D point, and marking as the third gray level If the vertical straight line extension line where the point D is located has an intersection point with the third pulse curve, and the gray level corresponding to the intersection pointD point is located on the first discharge pulse, otherwise D point is located on the second discharge pulse;
The data analysis unit pre-processes the partial discharge halftone image including:
The partial discharge halftone image is processed by an OTSU threshold segmentation method to obtain a binary image, and the OTSU algorithm calculates the inter-class variance To determine a threshold valueSo thatThe maximum, in the formula,、Is the duty ratio of two types of pixel points,、The average value of two types of pixel points;
Median filtering is carried out on the binary image, pixel information of the image is reserved, morphological expansion operation is carried out on the image after median filtering, and the area of an insulation failure area is obtained The expansion operation formula isIn which, in the process,As the original image is to be taken,Is a structural element;
Performing color reversal treatment on the partial discharge halftone image subjected to the first binarization segmentation to obtain a color reversal image, wherein the color reversal formula is as follows In which, in the process,For the pixel values of the original image,Is the pixel value of the image after the color reversal;
And positioning the pixel positions of the areas where the discharge pulse D points are positioned in the inverse color images, respectively marking and deleting to obtain residual inverse color images, performing median filtering on the residual inverse color images to obtain filtered inverse color images, and performing morphological filling operation on the filtered inverse color images to obtain filled inverse color images.
2. The nondestructive testing device for insulation performance of locomotive converter according to claim 1, wherein the coordinates of the rising edge and the falling edge of the partial discharge pulse detected by the second binarization segmentation are respectively recorded as A pointPoint BConnecting the points A and B to obtain a ray, and recording the equation of the ray asIn which, in the process,,。
3. The nondestructive testing device for insulation performance of locomotive converter according to claim 2, wherein the gray scale of the partial discharge gray scale image after the second binarization segmentation is set asCounting gray values of all pixel points between the point A and the point B of each discharge pulse, normalizing the gray values to normalize the pixel pointsThe value of the interval and the gray level corresponding to the pixel point are recorded asThe formula isIn which, in the process,Is the gray level corresponding to the pixel point,For any pixel of a partial discharge greyscale imageIs a gray value of (a).
4. A locomotive converter insulation performance nondestructive testing device according to claim 3, wherein the filtering of the partial discharge gray scale image by the image processing unit comprises:
Carrying out median filtering and mean filtering on the partial discharge gray level image subjected to the second binarization segmentation to obtain a filtered image, wherein a median filtering formula is as follows In which, in the process,For the pixel values of the original image,For the filtered image pixel values,The mean value filtering formula is as followsIn which, in the process,In order to filter the window size,,;
Obtaining local gray average value of filtered imageIn which, in the process,For filtered imageThe gray value at which the color is to be changed,For image size, according to the formulaCalculating local gray mean square valueAnd performing enhancement processing on the image.
5. The apparatus for non-destructive testing of insulation properties of a locomotive converter according to claim 4, wherein said data analysis unit further comprises:
Morphological corrosion operation is carried out on the filled anti-color image to obtain a corroded anti-color image, wherein the corrosion formula is that Performing inverse color treatment on the corroded inverse color image to obtain an image after inverse color treatment, performing morphological closing operation on the image after inverse color treatment to obtain an insulation breakdown speckle image, and performing median filtering on the insulation breakdown speckle image to obtain a filtered insulation breakdown speckle image;
Morphological filling operation is carried out on the filtered dielectric breakdown speckle image, and a communication area with the largest pixel point is obtained and is recorded as ,The number of the pixel points is recorded as the number of the pixelsThenThe pixel number of the region is the pixel number of the breakdown spot regionPixel count of area breakdown spot area,In the formula, ifThenAccording to the formulaCalculating the insulation breakdown rateWhen (when)If the voltage is larger than the preset breakdown threshold, judging that the insulation of the locomotive converter fails, wherein,Is the area of the insulating surface of the locomotive converter.
6. A nondestructive testing method for insulation performance of a locomotive converter, which is used for the nondestructive testing device for insulation performance of a locomotive converter according to claim 5, and is characterized by comprising the following steps:
s1, applying a partial discharge signal with preset intensity to a locomotive converter by using a detection device, and monitoring the partial discharge signal;
s2, carrying out Fourier transform on partial discharge signals fed back by the locomotive converter, and converting the partial discharge signals into partial discharge images;
S3, converting the partial discharge image into a partial discharge gray scale image, and further converting the partial discharge gray scale image into a partial discharge halftone image;
S4, preprocessing the partial discharge gray level image and the partial discharge halftone image;
S5, carrying out correlation analysis on the partial discharge gray level image and the partial discharge halftone image to obtain an analysis result, wherein in the correlation analysis, a correlation coefficient between the partial discharge gray level image and the partial discharge halftone image can be calculated:
;
In the formula, For the values of the corresponding pixels of the two images,Is the average value of the pixel values of the image;
And S6, displaying, storing and analyzing the analysis result, and outputting a final detection result of nondestructive detection of the insulation performance of the locomotive converter in a form of an image, so that a user can intuitively understand the insulation performance condition of the locomotive converter.
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