High-voltage insulation

R. W. Sorensen: My first point is in connection with the statement that we use our insulations under stresses which rarely exceed the breakdown voltage of air, though tests show a strength of 10 to 20 times that of air for many of the insulations used. This plea for a more strenuous use of insulating materials is interesting in the light of a request in another paper given this morning, in which the author recommends a decrease in the test voltage applied to transformers with one terminal grounded.