The relative importance of some factors influencing the impulse electric strength of 10-C oil

When uniform-field, impulse electric strength measurements were made in different laboratories on liquids having ostensibly the same composition, the resulting values of electric strength often differed by as much as a factor of seven. To resolve this discrepancy, a study of the problem revealed that differences in the following experimental conditions might be responsible for the divergence of results: (1) electrode shape and spacing; (2) electrode composition; (3) physical impurities in the liquid (e.g., dust content); (4) waveshape of the testing voltage; and (5) chemical impurities in the liquid samples. While the findings of Wilson (1) and Weber and Endicott (2) had demonstrated the importance of the electrode spacing and shape in determining the measured strength, it was desirable to make a survey of the relative importance of all these factors. The last named variable, viz., the effect of chemical impurities, was not investigated but merely held constant by using samples from the same batch of oil throughout the experiments. The experimental results are summarized.