Study Of Corona Discharge Based On The Processing Technology Of Digital Image

The first description of discharge appeared in gas discharge field was optical image,however, due to the difficulties of its quantitative detection, the current amount is detected mainly in the electrical signal, the light intensity signal, spectral signal, electromagnetic wave, ultrasonic, gas composition. Recently, due to the rapid development of digital image technology, the digital processing technology of optical image of gas discharge also receive attention, but interrelated studies focused on the ultraviolet image, the study of colorimetry mainly concentrated in the field of thermal plasma, less in the field of the visible and discharge plasma. Since visible light cameras have higher image resolution than ultraviolet imager, therefore the visible image contains richer spatial configuration information. This paper expands morphological study of corona discharge for the visible image, and does some preliminary exploration research on colorimetry.By researching on the morphological distribution of the quantitative indicators that gamma, standard deviation and coefficient of variation about the visible light image, we observe the "stem" shape spatial structure of the corona discharge on the image, and comparative analysis of the current pulse to describe the corona pilot discharge phenomenon in short gap, which also shows that digital image processing technology for morphological study of corona discharge is feasible.The specific achievements obtained are as follows:1) Under AC, in the long brush-like corona stage of the pointed tip electrode, that is the preliminary breakdown stage, the indicators that average gray level and standard deviation of the discharge image show platform-like change, which means the existence of "stem" structure in space, but other stages don't exist; these indicators are slowly varying in each discharge stage of the ball electrodes, and don't have platform-like change.2) Under DC, the "stem" structure exists in the long brush-like corona stage of the pointed tip electrode in positive polarity, but the negative polarity doesn't exist, neither do other stages and each discharge stage of ball head electrode, which confirme that the "stem" structure come from a positive polarity under AC voltage.3) In the case of AC, in the long brush-like corona stage of the pointed tip electrode,rising time of current pulse increases and is divided into two, but other stages don't exist;neither does each discharge stage of ball head electrode. Calculations show that these two speeds correspond to the speed of the pilot and the streamer that the head of the pilot. We believe that in a very non-uniform electric field, if the discharge occurs repeatedly in the same position, long brush-like corona will evolve into corona type pilot discharge.By researching on the colorimetry distribution of the quantitative indicators that gamma, standard deviation and coefficient of variation about the visible light image, we observed the trends of gamma's weight ratio of the three component diagram red(R),green(G), blue(B) that the true color image decomposed into, which can be used to describe the different stages of the discharge. Preliminary specification digital image processing technology used in the study of discharge colorimetry is feasible. The specific achievements obtained are as follows:1) In the case of AC, at different stages of corona discharge, the percentage of RGB components have changed, the Trends of corresponding gamma curve also have difference,which can be used to illustrate the extent of the development of AC corona discharge.2) In the case of DC, the proportion of the B and R component of the corona discharge image are opposite at the tip, which verifies the variation of the RGB components at different stages of corona discharge under the AC voltage.3) Under specific lighting conditions, when exposure time is constant, the curve of gray characteristic value can still characterize the stage of the development of the long brush corona discharge, but the specific light source would have an effect on the proportion of RGB components of the corona discharge image.4) In the process of increasing AC voltage, there is substantially no new spectral characteristic lines appear, their relationship with the visible images should be studied further.