Streamer propagation in seed based insulating oils under lightning impulse voltages

This paper is devoted to the streamers propagation in natural esters (vegetable oils) in a point - plane electrode arrangement stressed by standard lightning impulse voltage (1.2/50 μs). We mainly investigate the shape and stopping length of streamers as well as the associated current. Six commercial oils (untreated natural ester) extracted from grape seeds (GS), sunflower (SF) and rape seed (RS), corn (CO), rice (RI) and sesame (SS) that could constitute potential liquids for high voltage applications are tested. A mineral oil (MO) is also tested for comparison. It´s shown that the streamers are filamentary in the different oils for both polarities. For a given voltage, the stopping lengths (L_f) of streamers are longer when the point is positive than when it is negative; also, except mineral oil when the point is negative, the values of L_f are very close enough in all tested oils.