Test barrel devised for surge tests on oils

INSULATION co-ordination on oil-circuit-breaker designs makes desirable a knowledge of surge voltages required to break down insulating oils. Because of the lack of available data on this subject a series of tests using hemispherical electrodes has been under way during the past year at the California Institute of Technology, Pasadena. One reason for the absence of data of this type, according to R. W. Sorensen (A´07, F´19) professor of electrical engineering at that institution, has been the difficulty in providing a convenient lead-in bushing for making the necessary tests. This difficulty was overcome by making a test barrel in which the electrodes were mounted, with a lead-in bushing of insulating material having about the same dielectric constant as insulating oil. Professor Sorensen has made available the following brief description of the test barrel.