Breakdown and prebreakdown phenomena in liquids

Abstract

In this paper we present a comprehensive account of our results on streamer propagation in dielectric fluids in point-plane geometries. Propagation velocities for both positive and negative streamers have been determined as a function of the following parameters: temperature, pressure, density, viscosity, composition, and conductivity. Effects of voltage and interelectrode spacing were examined. Current and light emission during streamer growth were measured. The relation between shock wave and streamer velocities was investigated. Small concentrations of low-ionization potential additives markedly accelerated the positive streamers, while electron scavengers accelerated the negative streamers. Mechanisms to account for these observations are discussed.

Spatially and temporally resolved electron density measurements in streamers in dielectric liquids

“…The streamer current is mainly carried by the electrons while positive ions, created at the streamer tip due to field ionization [19] and in the filament due to impact ionization by the electron current, can be considered stationary in terms of their motion in the streamer propagation direction. A net charge of positive ions is thus accumulated in the filament.…”

Optical observation of streamer propagation and breakdown in seed based insulating oil under impulse voltages

“…It has been reported earlier in their pioneer work by Devins et al (1981) and later by others ( Yasuda et al, 2010;Chadband and Sufian, 1985;Nelson, 1980;Kelley and Hebner, 1981) that the electron affinity of liquid molecules played a dominant role in the propagation of streamers. The molecule of Canola oil contains three esters (−C OOR) which have electro-negative oxygen atoms.…”

“…Their composition varies depending on the source, and the aromatic content plays a major role in the formulation of the streamer shapes (Badent et al, 2000;Devins et al, 1981). Some salient properties of these oils were measured in the laboratory and are summarized in Table 1.…”

Effect of Fe3O4 nanoparticles on positive streamer propagation in transformer oil

“…Streamers are low density conductive structures formed in the overstressed regions of transformer oil, whose propagation behavior is closely related to field dependent ionization of transformer oil. 2,18 In this study, applied electrical field is same in both pure oil and nanofluids. So, the observed dramatically changes in both propagation velocity and shape of positive streamers in Fe 3 O 4 nanofluids could be attributed to the change of space-charge field distribution induced by nanoparticles.…”