Positive streamer propagation in large oil gaps: experimental characterization of propagation modes

TLDR

The study experimentally investigates positive streamer propagation in mineral oil across large point‑plane gaps under impulse voltage. The authors performed systematic experiments varying gap distance up to 35 cm and applied voltage, measuring breakdown voltage, time to breakdown, streamer visualization, transient current, charge, and light emission intensity. Streamers were classified into 2nd, 3rd, and 4th modes with velocities exceeding 100 km/s, and mode transitions correlated with applied voltage, charge, and shape, revealing underlying mechanisms and practical implications.

Abstract

This paper presents an experimental study of positive streamer propagation in mineral oil, in large point-plane gaps under impulse voltage. A systematic investigation was done concerning the influence of gap distance (/spl les/35 cm), and voltage from streamer inception up to large overvoltages. The measurements presented concern breakdown voltage measurements, time to breakdown, visualization of streamers (streak and still photographs), electrical measurements (transient current, charge), light emission intensity. Streamers are characterized and then classified into different modes (2nd, 3rd and 4th modes) according to their propagation velocities up to more than 100 km/s. According to the applied voltage, transitions between modes are observed, and correlations are established between charge, shape, and streamer velocity. The physical mechanisms as well as practical consequences are then discussed.