Streamer Simulation in Nano-Based Dielectric Fluids at Different Fe3O4 Nanoparticle Concentrations

Nano-based dielectric fluids (NDF) seem to be a good alternative for improving dielectric and thermal characteristics of conventional liquid dielectric systems used in power transformers. Fe₃O₄ (magnetite) nanoparticles (NP) is one of the most investigated type of NP. Some experiments have shown that with its addition to mineral oil (MO) and ester, increases in breakdown voltage (BV) can be achieved applying both AC and DC voltages. This kind of NP have the advantage that can be handled and synthesized safely and easily using a two-steps method. Besides, streamer propagation can be reduced or avoided introducing Fe₃O₄ NP in dielectric fluids. These NP act as electronic traps and behave like slow-moving charged particles in the NDF. This behaviour as well as other dielectric characteristics such as resistivity, permittivity and loss tangent, depend on the type, size and concentration of NP. In this work, comparisons and analyses of thermal and dielectric performance of NDF with different Fe₃O₄ NP concentration are made taking into account the evolution and behaviour of streamers. It has been found that temperature in streamer tip, its length and speed depend on the Fe₃O₄ NP concentration and the BV is affected because of changes in streamer speed. The most adequate concentration for controlling the streamer has been obtained through simulations and comparisons with experimental results showing good agreement.

I. Introduction

Nano-based dielectric fluids (NDF) are used for improving thermal and electrical characteristics of conventional liquid dielectric systems such as mineral oil (MO) and ester. Additionally, NDF can improve the power density and reliability in power transformers and other important equipment for the power systems. Nanoparticles (NP) immersed in dielectric fluids can produce a reduction on the charge density inside the NDF and create a lower and uniform internal electric field, which indeed gives a reduction on the partial discharges (PD) occurrence. The addition of conductive particles increases the thermal conductivity even at low concentrations [1].