Conduction current pulses in organic insulating liquids under electrical stress

The mean square values of conduction current fluctuations in organic insulating liquids under high direct electrical stresses were measured by customary noise measurement methods. The effect of dissolved air, oxygen and nitrogen was studied, as well as that of anthraquinone which is known to have an important effect on the gassing properties of transformer oil. Both uniform and non-uniform electrode configurations were used, and pulses in liquid paraffin, one of the main constituents of transformer oil, were also investigated. It was shown that the presence of limited quantities of air and especially oxygen had an important influence on the magnitude and the pattern of the conduction current pulses in insulating liquids. The role of the unsaturated organic constituents of transformer oil in improving its behaviour under electrical stress seemed also to be clearly indicated.