POSITIVE STREAMER PROPAGATION IN LARGE OIL GAPS - ELECTRICAL-PROPERTIES OF STREAMERS

This paper presents experimental data and calculations concerning the electrical properties of positive streamers in mineral oil at large ga ps and Hv. The experiments concern the measurement of charge, electric field, and the determination of the potential drop along streamers, e ither in the liquid alone, or for streamers guided within insulating t ubes. Calculations of charge and field distribution around streamers a re carried out by charge simulation. To do this, streamers are represe nted by objects with simple shapes (spheres or cylinders) equivalent t o their macroscopic aspect. These models lead to a correct agreement w ith measured Streamer charge and field on the plane electrode. Qualita tive correlations are established between calculated field distributio ns and streamer behavior such as velocity, transitions between propaga tion modes. It is also concluded that the potential drop in streamers and branching both act as regulating mechanisms that help to keep the streamer tip field, and hence the velocity, constant over a wide volta ge range.