Study of discharge in air from the tip of an icicle

Electric discharge between the tip of an icicle and a plane electrode has been studied because of its relevance to the flashover of high voltage ice-covered insulators. A photomultiplier was used to scan the high voltage rod simultaneously with current measurement technique. The basic properties of streamers, namely the onset voltage, leakage current, mean propagation velocity and breakdown voltage, have been measured and compared with propagation from a metal rod as a reference. The effects of several experimental parameters such as freezing water conductivity, surrounding temperature and air gap length on the discharge characteristics have been examined. Possible mechanisms, which control discharges from ice points, have also been discussed and empirical relationships to predict breakdown voltage have been derived.