Influence of solid dielectric on the impulse discharge behaviour in a needle-to-plane air gap

Abstract

The structure of the streamer zone of an impulse discharge of positive polarity in a needle-to-plane air gap is observed with high spatial resolution for two cases: for gaps with and without a thin dielectric plate (barrier) placed along or at a certain distance to the gap axis. The experiments are carried out with two amplitudes and shapes of the applied voltage pulse (impulse length about 800 and 360 ns). The discharge structure is analysed using a CCD camera and dust figure technique. It is shown that the discharge characteristics such as shape and amplitude of the discharge current, the streamer zone length and structure depend on the permittivity of the barrier, its thickness, its surface state and its position relative to the needle electrode. With a closer position the influence of the barrier is more pronounced, but in all cases of the barrier present in the gap, including the case when the barrier touches the needle electrode, a volume part of the discharge is detected in addition to the surface discharge. The structure of the streamer zone of the discharge at different conditions is analysed.

Effect of inhomogeneities on streamer propagation: I. Intersection with isolated bubbles and particles

“…For example, E/N at the streamer tip is 1100 Td approaching the negative bubble and 1300 Td for the positive bubble. The corresponding values of electron density and T e are 1.7 × 10 14 cm −3 and 7.1 eV for the negative bubble and 3.7×10 14 cm −3 and 7.5 eV for the positive bubble. After passing the off axis positive bubble the streamer regains its unperturbed form.…”

Characteristics of streamer propagation along the insulation surface: influence of dielectric material

“…Some researchers also used Fractal Geometry and Monte Carlo method to simulate its characteristics [21][22][23][24]. Compared with research on the streamer propagation in air, only several articles investigated the streamer propagation along the insulation surface [25][26][27][28][29][30][31]. The characteristics of streamer propagation in air and along the different dielectric materials were surveyed in [25][26][27][28][29].…”

Streamer dynamics in gases containing dust particles

“…In this case electron avalanche in front of the streamer head is enhanced by the presence of a dielectric due to electron emission from the surface produced by photons emitted by the discharge [10]. The higher rate of electron avalanche increases the speed of the streamer.…”