FORMATION AND CHARACTER OF THE IMPULSE BREAKDOWN IN TRANSFORMER OIL.

Tests with lightning and switching impulses in transformer oil were conducted and revealed, from certain aspects, new features of the breakdown process as demonstrated by selected photographs and motion films. An attempt is made to theoretically support the experimental results described in this paper. A strong electric field seems to initiate bubble formation and, in a uniform field, a great number of bubbles will be produced simultaneously within the entire bulk of the liquid. The subsequent ionization of many independent bubbles, and their connection by electron avalanches builds up a chain, along which a spark, bridging the distance between the electrodes, will develop. The structure of the breakdown arc reveals that no channel of uniform character is formed, high current intensity occurs only within the individual bubble, while these remain separate during and after the entire process.