Measurement of dielectric properties of solids at cryogenic temperatures

Abstract

Investigations of dielectric properties of a range of solid insulating materials between ambient and liquid helium temperatures were carried out. It has been demonstrated that the partial-discharge activities were greatly reduced when the temperature was lowered. In addition, considerable improvements in the electric strength and the life-time of the insulation under alternating, impulse and direct voltages; and for voltages with polarity reversal were obtained. A correlation between the discharge activities and the electric strength and life-time was tried. Measurement of loss-tangent and permittivity for polymers showed significant reduction at low temperatures whereas for impregnated-paper and impregnating compound lossregions were observed. The mechanical response of these materials proved to be suitable as electrical insulation for equipment at cryogenic temperatures.