The effect of load break switching in silicone

The needle-plane breakdown properties of silicone and mineral oil were determined and compared. Partial discharge currents were under 10 mA. These low-level arcing conditions in silicone caused scission and crosslinking of the material, forming a silicone gel around the electrodes. In the absence of data more relevant to the behavior of silicone transformer liquid exposed to high energy arcing, the low-level partial discharge data have been extrapolated to predict massive gelation if silicone were used in oil-immersed switches. Findings are introduced from full-scale tests which indicate that extrapolation of the low-level partial discharge data does not correctly predict the effect of arcing caused by switching currents of up to 300 A under silicone transformer liquid