Effects of nanoparticle charging on streamer development in transformer oil-based nanofluids

Abstract

Articles you may be interested inDielectric response of transformer oil based ferrofluid in low frequency range J. Appl. Phys. 114, 034313 (2013); 10.1063/1.4816012 Effect of nanoparticle polarization on relative permittivity of transformer oil-based nanofluids Iron oxide nanoparticles fabricated by electric explosion of wire: focus on magnetic nanofluids AIP Advances 2, 022154 (2012); 10.1063/1.4730405Effect of electron shallow trap on breakdown performance of transformer oil-based nanofluids Transformer oil-based nanofluids with conductive nanoparticle suspensions defy conventional wisdom as past experimental work showed that such nanofluids have substantially higher positive voltage breakdown levels with slower positive streamer velocities than that of pure transformer oil. This paradoxical superior electrical breakdown performance compared to that of pure oil is due to the electron charging of the nanoparticles to convert fast electrons from field ionization to slow negatively charged nanoparticle charge carriers with effective mobility reduction by a factor of about 1 ϫ 10 5 . The charging dynamics of a nanoparticle in transformer oil with both infinite and finite conductivities shows that this electron trapping is the cause of the decrease in positive streamer velocity, resulting in higher electrical breakdown strength. Analysis derives the electric field in the vicinity of the nanoparticles, electron trajectories on electric field lines that charge nanoparticles, and expressions for the charging characteristics of the nanoparticles as a function of time and dielectric permittivity and conductivity of nanoparticles and the surrounding transformer oil. This charged nanoparticle model is used with a comprehensive electrodynamic analysis for the charge generation, recombination, and transport of positive and negative ions, electrons, and charged nanoparticles between a positive high voltage sharp needle electrode and a large spherical ground electrode. Case studies show that transformer oil molecular ionization without nanoparticles cause an electric field and space charge wave to propagate between electrodes, generating heat that can cause transformer oil to vaporize, creating the positive streamer. With nanoparticles as electron scavengers, the speed of the streamer is reduced, offering improved high voltage equipment performance and reliability.

Effect of Fe3O4 nanoparticles on positive streamer propagation in transformer oil

“…10 An electron-scavenging model is proposed and generally used to explain these phenomena based on modeling the electrodynamic process in Fe 3 nanofluids. 8,9,11 Some researchers think the potential well generated by induced or polarized charges on the surface of nanoparticles can capture the passing electrons and enhance the breakdown performance of transformer oil. 10,12 In comparison with the dielectric breakdown strength of nanofluid, its prebreakdown streamer propagation behavior is more important to understand the fundamental modification effect of nanoparticle, which can give valuable insight into the events leading to breakdown.…”

AC Magnetic Susceptibility of Ferrofluids Exposed to an External Electric Field

“…Many studies showed that these ferrofluids withstand higher voltages than pure transformer oils, the property often presented as a paradox [3,4]. In this context, a theoretical modelling has indicated that nanoparticles in transformer oil can act as free charge scavengers which slow down the streamer velocity leading to dielectric breakdown [5]. Therefore, the mobility of SNP also plays an important role in reducing the streamer velocity.…”

FE Analysis of Plasma Discharge and Sheath Characterization in Dry Etching Reactor

“…In this paper, we proposed a full finite element approach where the charge transport equations of hydrodynamic diffusion-drift model and the electric field equation were numerically solved in a fully coupled system by using a standard finite element procedure for transient analysis [7][8][9][10][11]. Numerical technique for the hydrodynamic diffusiondrift modeling using charge transport equations is used in various applications such as corona discharge, heat transfer and cooling effect of heavy electric machines [12][13][14].…”