Abstract :
Experiments have been carried out to investigate the conductivity and power factor of transformer oil at high stresses. It has been found that the relation between the applied voltage (V) and the conduction current (I) under direct stresses between 50 and 300 volts per mil can be expressed by the equation I = kVm, where m is approximately 3. At stresses between 50 and 120 volts per mil, the relation may be expressed more accurately by the equation V = V0 + nI. The specific resistance of pure transformer oil at a stress of 50 volts per mil is greater than 4 × 109 megohms per cm cube. The power factor of pure transformer oil is of the order of 0.00005 at stresses under 70 volts per mil (r.m.s.), but above this stress is increases rapidly. It is suggested that the observed results can be explained by a theory of ionization by collision at high stresses.
