Colorimetric Method for Discharge Status Diagnostics Based on Optical Spectroscopy and Digital Images

Discharge is a process, which involves changes in multiple species, and it is important for researchers to be able to describe changes in discharge status holistically. In this study, we applied AC and DC high voltage power sources to a short-gap needle-plane device in an atmospheric environment. We propose two new corona diagnosis methods based on spectral data and visible images. The experimental results demonstrate that, in the RGB system, the proportion of the blue component in AC corona images has the characteristic of decrease-stable-increase with voltage, and the corresponding result of the spectra is stable-increase. In the XYZ system, the AC corona chromaticity coordinates of both images and spectra demonstrate a linear fitting result with the voltage, and the image results contain a retracement process, showing shows the increase-stable-decrease trend of chromaticity coordinates x and y, which correlates well with oscilloscope results. The difference between the image and spectra results indicates that, compared to the spectra, high-resolution visible images are more sensitive to imperceptible changes in colorimetry information. The change of DC corona colorimetry characteristics can illustrate the change in AC corona colorimetry characteristics. Additionally, the dominant wavelength is proven to reflect the discharge species, and can reflect the vibrational temperatures. To the best of our knowledge, this paper represents the first attempt to systematically introduce colorimetry theory into discharge images and spectra. We successfully obtained colorimetric indicators with the linearity and low-dimension characteristics, which correspond well with known physical parameters.