Breakdown phenomena of long gaps under switching impulse conditions influence of distance and voltage level

The influence of the different phases of the discharge on the statistics of the breakdown processes has been investigated in a wide range of gap lengths (from 2 to 10 m) and applied voltage levels. The effect of the field distribution, along the gap and of the overvoltage ratio upon the development of each discharge phase, has been studied and the transition between subsequent phases has been analysed. The experimental results have been compared with theoretical predictions; the satisfactory agreement, which has been obtained indicates that the theoretical simulation of the discharge phenomena is relatively advanced and starts to be useful from a engineering point of view.