Cathode Root Motion Studies of High Current Arcs Using an Optical Fiber Array Based Imaging System

An integrated portable measurement system is presented for the study of high speed and high temperature unsteady plasma flows such as those found in the vicinity of high current switching arcs. The system permits direct and nonintrusive measurement of arc light emission images with a capture rate of 1 million images per second (1MHz), and 8 bit intensity resolution. Novel software techniques are reported to visualise the arc motion and to measure arc trajectories. Results are presented on high current (2kA) discharge events where the electrode and arc runner surfaces are investigated using optical surface scanning methods; such that the position of the arc roots on the runner can be correlated to the measured trajectories. The results show evidence of the cathode arc root stepping along the arc runners.