Surge-voltage breakdown characteristics for electrical gaps in oil

This paper, emanating from a request for information regarding surge voltages required to break down gaps in oil, gives surge breakdown voltage values with different gap spacings for ¼-inch, ½-inch, and 1-inch round rod electrodes with hemispherical ends immersed in transformer oil. As expected, these values are a function of “time to breakdown” but for each condition curves show constant breakdown values for breakdown times of the order of about 16 microseconds and longer with the 1½ × 40 negative wave, used on all the tests reported. Particular attention is called to the relatively small amount of oil required for tests of this type, made possible by the special type of test barrel used.