Abstract: The problem of insulation damage from partial discharges below the so-called inception voltage has not attracted much attention from the insulation community. Indications of possible damage exist from previous research. In the present paper, the possibility of existence of such phenomena is investigated with small air gaps and non-uniform electrode arrangements. It is shown that random discharges below inception voltage exist, which on occasions can be quite numerous. Such discharges are registered and their implications are discussed.
Keywords: Small air gaps, inception voltage, partial discharges, non-uniform electrode arrangement.