电晕放电的数字图像处理技术研究

发布时间：2018-04-11 15:49

本文选题：电晕放电 + 形态学　；参考：《华中科技大学》2016年硕士论文

【摘要】：气体放电领域最早出现的放电描述是光学图像,但由于其定量检测的困难,目前的检测量主要集中在电信号、光强信号、光谱信号、电磁波、超声波、气体成分等方面。近来由于数字成像技术的高速发展,气体放电光学图像数字处理技术也得到重视,但相关研究主要集中在紫外图像上,色度学的研究又主要集中在热等离子体领域,在可见光波段和放电等离子体领域研究较少。由于可见光相机比紫外成像仪有更高的图像分辨率,因此可见光图像包含更加丰富的空间结构信息。本文针对电晕放电的可见光波段图像展开形态学研究,并在色度学方面做了一些初步探索。通过研究可见光图像灰度系数,标准差和变异系数等定量指标的形态学分布,观察到电晕放电图像上的“茎”状空间结构,以及电流脉冲分析对比说明在短间隙放电中存在电晕型先导放电现象,这也说明数字图像处理技术用于放电形态学研究是可行的。取得的具体成果如下:1)在交流情况下,在尖头电极长刷状电晕阶段,即预击穿阶段,图像的平均灰度和标准差指标呈现平台状变化,意味着在空间上存在“茎”结构,而其他阶段没有;在球头电极各放电阶段这些指标均缓慢变化,无平台状变化;2)在直流情况下,正极性尖头电极长刷状电晕阶段,存在“茎”结构,负极性没有,其他阶段都没有;球头电极各放电阶段都没有,证实了交流电压下,“茎”结构来自于正极性;3)在交流情况下,发现在尖头电极长刷状电晕阶段,电流脉冲上升沿时间增加且分为两段的现象,其他阶段没有;球头电极各放电阶段没有此现象。计算表明这两段的速度是和先导速度以及先导头部的流注速度对应。我们认为在极不均匀电场中,如果放电反复在同一位置发生,长刷状电晕就会演变成电晕型先导放电。通过研究可见光图像灰度系数,标准差和变异系数等定量指标的色度学分布,观察到真彩图像分解成的红(R)、绿(G)、蓝(B)三种分量图的灰度系数分量比例的变化趋势,可用于描述放电不同阶段。初步说明数字图像处理技术用于放电色度学研究是可行的。取得的具体成果如下:1)在交流情况下,电晕放电在不同阶段,RGB分量图所占的比例发生了变化,对应的灰度系数曲线的变化趋势也产生了差异,这一现象可用于说明交流电晕放电的发展程度;2)在直流情况下,电晕放电图像的RGB分量中B分量和R分量在针尖处所占比例正好相反,这验证了交流电压下,电晕放电不同阶段RGB分量图的变化规律;3)特定光照条件下,曝光时间一定时,灰度特征值曲线依旧可以表征长刷状电晕放电的发展阶段,但外界特定光源会对电晕放电图像的RGB各分量所占比例产生影响;4)在交流电压增加的过程中,电晕放电的光谱基本没有新的特征谱线出现,其与可见光图像的关系有待进一步研究。
[Abstract]:The earliest description of discharge in the field of gas discharge is optical image. However, due to the difficulty of quantitative detection, the current detection and measurement mainly focus on electrical signal, light intensity signal, spectral signal, electromagnetic wave, ultrasonic wave, gas composition and so on.Recently, due to the rapid development of digital imaging technology, the digital processing technology of gas discharge optical image has been paid more attention to, but the related research is mainly focused on ultraviolet image, and the chrominance research is mainly focused on the field of thermal plasma.There are few studies on visible light and discharge plasma.Because the visible camera has higher resolution than the ultraviolet imager, the visible image contains more spatial structure information.In this paper, morphological studies on visible wave images of corona discharge have been carried out, and some preliminary studies on chromaticity have been made.The "stem" spatial structure of corona discharge image was observed by studying the morphological distribution of quantitative indexes such as gray coefficient, standard deviation and variation coefficient of visible light image.The comparison of current pulse analysis shows that there is a corona pilot discharge phenomenon in short gap discharge, which also shows that digital image processing is feasible for the study of discharge morphology.The concrete results obtained are as follows: 1: 1) in the case of AC, in the long brush corona stage of the tip electrode, that is, the pre-breakdown stage, the average gray scale and standard deviation of the image show a platform-like change, which means that there is a "stem" structure in space.But not in other stages; in each discharge stage of the spherical electrode, these indexes all changed slowly, and there was no platform-shaped change. In the DC case, there was a "stem" structure and no negative polarity in the long brush corona stage of the positive electrode.None of the other stages; none at all the discharge stages of the spherical electrode, which confirms that the "stem" structure comes from the positive electrode at AC voltage) in the AC case, at the long brush corona stage of the pointed electrode,The rising time of current pulse increases and is divided into two stages, but not in other stages, but not in each discharge stage of the spherical electrode.The results show that the velocity of the two segments corresponds to the velocity of the pilot and the velocity of the flow at the head of the pilot.It is considered that in an extremely inhomogeneous electric field, if the discharge occurs repeatedly in the same position, the long brush-shaped corona will evolve into a corona type of lead discharge.By studying the chromaticity distribution of the quantitative indexes such as gray coefficient, standard deviation and variation coefficient of visible light image, the change trend of gray coefficient component proportion of the three kinds of components of the true color image is observed.It can be used to describe different stages of discharge.It is shown that the digital image processing technique is feasible for the study of discharge chromaticity.The specific results obtained are as follows: (1) in the case of AC, the proportion of corona discharge in the RGB component map has changed in different stages, and the change trend of the corresponding gray coefficient curve has also been different.This phenomenon can be used to explain the degree of development of AC corona discharge. In DC case, the ratio of B component and R component in the RGB component of the corona discharge image is exactly the opposite at the tip of the needle, which verifies that under the AC voltage, the ratio of B component and R component in the RGB component of the corona discharge image is exactly the opposite.The variation of RGB component diagram in different stages of corona discharge. (3) when exposure time is fixed, the gray level eigenvalue curve can still represent the development stage of long brush corona discharge.However, specific external light sources have an effect on the proportion of RGB components in corona discharge images. (4) in the process of increasing AC voltage, there are basically no new characteristic lines in the spectrum of corona discharge.The relationship between it and visible image needs further study.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TP391.41;O461.2

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