Thermal Breakdown of Silicone Liquids under Pulsed High-Frequency Field

The effects of the pulse duration of applied field and electrode geometry on the thermal-breakdown phenomenon have been studied by applying pulsed high-frequency field (1-10 MHz) with variable duration (10-1000, μs) to the silicone liquids immersed in the rod-plane electrodes (approximate uniform field) and the needle-plane electrodes (extreme nonuniform field), considering the temperature dependence of the electrical conductivity of silicone. It has been found that the thermal breakdown due to dielectric heating occurs when the field is applied for less than a millisecond. Thermal breakdown explains the experimental results in which the breakdown strength decreases in the rod-plane electrodes with increasing pulse duration and electrode separation, but is little influenced in the needle-plane electrodes by these same variables.