Evolution of AC and DC Arcs in Vacuum Circuit Breaker: An Image Processing Study

The evolution of AC arc and DC interruption,in the glass vacuum circuit breaker(VCB)without metal shield,was investigated with high speed charge-coupled device(CCD)video-camera.The original work was the modification of double-threshold gray image segmentation algorithm in image processing.In the self-defined hottest plasma glow discharge,observable arc-spreading and background regions,the characteristics of the images,including the arc-diameter,high intensity area,and ratio of high-intensity to observable arc-spreading areas,were calculated.The results show that the evolution of AC and DC arcs was significantly different.For example,in the axial magnetic field,the AC-arc intensity steadily and continuously decreased to extinguishing after an initial high-intensity diffusion for 2 ms;in contrast,after an initial high-intensity diffusion for only 1 ms,the DC-arc intensity abruptly decreased to extinguishing because of the injected commutation current.