The electric strength of transformer oil

The paper gives results of electric breakdown tests on transformer oil, made with direct and alternating voltages and with impulses of different durations. The dried oil used in these tests was filtered and carefully degassed in a closed test apparatus which incorporated the test cell. The oil treated in this way was tested with uniform and non-uniform electrode configurations, and a number of factors which influence the electric strength of the treated oil were examined. With the electric strength of the treated oil as a reference, the effect on its value was examined when a number of different impurities were added to the treated oil.Finally, a theory of the electric breakdown of this type of liquid is suggested which conforms to the experimental observations reasonably well.