A review of recent investigations into electrical conduction and breakdown of dielectric liquids

Recent work concerning electrical breakdown and conduction in dielectric liquids is reviewed. Particular emphasis is given to liquids of simple molecular structure although reference is made to some investigations using complex oils where the results obtained are also applicable to other liquids. Conduction measurements have been extended to fields up to 1.3 MV cm -1 using microsecond pulse techniques, and under these conditions very large currents are observed. The evidence concerning a collision ionization process is conflicting. Negative ion mobility measurements have been reported for fields of 500 kv cm -1 in n -hexane, and both the positive and negative ion mobilities in superfluid liquid helium have been thoroughly investigated. Electrical breakdown of liquid argon has revealed pronounced electrode effects, and the influence of the anode is particularly emphasized. Dissolved oxygen is found to increase the strength of a liquid and to give rise to a number of effects which can be explained by assuming the formation of space charge layers at the electrodes. Recent measurements of formative and statistical time lags in n -hexane have shown that previous interpretations were frequently incorrect.