Study On Image Processing And Parameterization Of DC Interruption Arc

In DC transmission and distribution system,vacuum circuit breaker bears the burden of quickly breaking short-circuit current.Its core function is to extinguish the vacuum arc caused by the separation of contacts,the evolution of vacuum arc has an important influence on the breaking capacity of vacuum circuit breaker.In this paper,the vacuum arc in DC interruption is taken as the research object,the motion characteristics and image parameterization of the vacuum arc are studied by using image processing technology.Firstly,the DC interruption experiment platform based on active commutation method is improved,and the control circuit of commutation source switching operation mechanism is redesigned,which greatly simplifies the use of components.By measuring the displacement curve of the main circuit breaker,the capacitor pre-charging voltage is set to 500 V according to the experimental requirements.The voltage and current waveform of interruption process is obtained.Secondly,a series of vacuum arc images were captured by using CMOS high-speed camera on the DC interruption experimental platform.Typical arcing process is analyzed by combining the arc voltage and current waveform.At the same time,the vacuum arc image is pre-processed,and the denoising performance of different algorithms is compared and analyzed with the PSNR as the index.Then,the vacuum arc image is segmented.The true-color image segmentation algorithm based on K-means clustering can extract the arc area from the whole picture more accurately.The pseudo-color image enhancement algorithm based on gray-level hierarchical method can make the arc image more in line with human visual characteristics.An improved double-threshold image segmentation algorithm is proposed.By comparing the vacuum arc images processed by different algorithms,it is found that the improved double threshold segmentation algorithm is more suitable for arc image segmentation.Finally,the true-color image segmentation algorithm and the pseudo-color image enhancement algorithm are used to describe the motion of vacuum arc.The results show that the DC interrupting arc first undergoes a rapid diffusion process after arc ignition,then extinguished rapidly due to the inject of commutation current.During commutation,the change of arc shape lags behind the change of arc current,and the position of arc extinction is near the arc igniton position.The improved double threshold segmentation algorithm is applied to the image.Three characteristics: arc diameter,area and area ratio of high gray value area of arc are extracted.The results show that about 1 ms after arc ignition,the arc expansion speed and area ratio of high gray value area of DC interrupting arc are higher than those of the following arcing process,while the area of high gray value area keeps linear growth.