Fractal analysis of streamer patterns in dielectric liquids under dc voltage

In order to investigate the streamers propagating characteristics with in a dielectric liquid, an equivalent electrical network was used to model branching streamers. Streamer patterns were computed to be applied for the fractal analysis on streamer. In this paper, the fractal dimension of streamer patterns in transformer oil was estimated based on box-counting. Streamer patterns were obtained from initiation stage to breakdown stage, in a 5, 10, 15 and 35 mm needle-to-plane gap, under a dc voltage of 30 kV and evaluated with 2D box count. Results indicate that the variation of fractal dimension with propagation times, widely different conditions of gap distance and streamer conductivity follows the similar trend to streamer length and area electrode gap.