Propagation of streamers in mineral oil at large distances

This paper presents an experimental study of the propagation of positive and negative streamers in mineral oil at large distances (up to 35 cm) in point-plane geometry under impulse voltage. This study of prebreakdown phenomena in oil at large distances has permitted establishment of the following facts: i) in positive polarity, phenomena are qualitatively similar to those observed at shorter distance - no transition or discontinuity of events due to an increase of the distance to 35cm has been observed; ii) in negative polarity, breakdown voltages in divergent fields in mineral oil under long duration impulses remain higher than in positive polarity for distances up to 35 cm. In this polarity prebreakdown phenomena present many qualitative similarities with those observed in positive polarity (continuously luminous propagating head, periodic reilluminations)