Arc-Column Contraction of Falling Peak-Current in Vacuum Circuit Breaker: An Experimental Study

Contraction of arc column, at the initial stage of arc distinguishing in vacuum circuit breaker, was experimentally studied with a high-speed charge coupled device (CCD) video camera to understand the correlation between the arc-shape's evolution on the arc-extinguish behavior and dielectric recovery. The arc column edges were extracted via image processing in Harris corner detection algorithm and by feature extraction technology. The time dependent diameter of arc column, in 5. 5~7. 4 ms within 155~20 pixels, was evaluated by data analysis; and by 3 rd-order polynomial data-fitting, the arc column contraction went through two distinctive modes:the diameter first decreased roughly at a steady rate from 6. 0 to 6. 7 ms, and then (after 6. 7 ms), rapidly shrank, simply because of the magnetic field, contraction of arc itself and gas pressure. Possible mechanisms explaining the arc-shape growth were also tentatively discussed in a thought provoking way.