Streamer discharge propagation and branching characteristics in transformer oil under AC voltage: Partial discharge and light emission

This paper describes an experimental study of streamer inception and propagation characteristics from a protrusion in transformer oil under AC voltage. The information acquired by partial discharge detection, such as current pulse sequences, phase-resolved PD (PRPD) pattern and statistical parameters are obtained; moreover, optical properties of streamer in transformer oil are captured by fast-imaging technique. The experimental results show that the pulse sequences represent different mechanisms. The stopping length of streamer are highly dependent on the amplitude of applied voltage. Both PRPD patterns and the shapes of streamer indicate that the positive and negative streamers show a strong polarity effect under AC voltage. The space charges formed periodically at the alternative half cycle of high voltage are responsible for the phenomena in the experiments.