Studies on temperature dependent dielectric properties of some insulators down to liquid helium temperatures

The work discusses on the behavior of dielectric properties of various commercially available insulators with respect to temperature (4.2 K to 300 K) and operating frequency range of 2.52 KHz to 500 KHz. A conventional parallel plate-based capacitor setup was designed and developed considering various conditions. The dielectric constant was found to be very dependent on the pre-breakdown partial discharges at low temperatures. At 4.2 K the discharges move far away from the electrodes and exert high electric stress on the sample under test, which results in the breakdown or the decrease in the dielectric strength. The relative permittivity (${ϵ}_r$) also decreased rapidly with the increase in frequency in most of the samples, this decrease is due to the reduction of space charge polarization effect. The correlation between the dielectric properties, operating frequencies and temperature have been studied in detailed.