Silicone gel is widely used to encapsulate power electronic circuits. The weakness in the electrical insulation is surface discharges initiating at the gel-substrate-electrode triple point. In this study, in order to understand the effect of electrode polarity on surface discharges, full-wave rectified voltage of both polarities are applied. It turns out that the cavity created by discharges propagates due to positive streamers regardless of the voltage polarity. Owing to the finite resistivity of gel and gel-substrate interface, surface discharges are rather characterized by peak-to-peak value of the applied voltage than the peak voltage.
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