Dielectric Properties of Cryogenic Liquids

Electric-breakdown measurements at 60 Hz have been made with cryogenic liquids-nitrogen, hydrogen, and helium. All of the cryogenic liquids have higher breakdown voltages than conventional transformer oil, except liquid helium which breaks down at a considerably lower voltage. The measured values of dielectric constant for the cryogenic liquids agree quite well with the published literature. The dissipation factor of the cryogenic liquids is so low that true values cannot be reported. They appear to be below 0.000001. However, by comparison of the indicated values, it appears that the dissipation factor of liquid helium may be about ten times that of liquid hydrogen.