AC breakdown voltage of Fe₃O₄based nanodielectric fluids. Part 2: Analysis of fluids with high moisture content

Abstract

The interest in developing new nanodielectric fluids suitable for electrotechnical applications has increased significantly in the last decade. Several authors have reported experiences on fluids manufactured using different base fluids and nanoparticles. Most of these studies are focused on the comparison of the thermal and dielectric properties of the nanofluids and the base liquids and most authors have found that the addition of nanoparticles to insulating liquids can lead to an improvement of their dielectric properties. This two-part paper analyzes the enhancement of the AC breakdown voltage of several nanodielectric fluids prepared by dispersing variable concentrations of Fe3O4 nanoparticles in a mineral oil. In the first part of the study, the performance of fluids that had been previously dried and degasified were tested. In the second part of the study the impact of the presence of moisture in the dielectric strength of the liquids is analyzed trying to get insight into the physical mechanisms that justify the observed enhancements when nanoparticles are added to insulating liquids.

Dielectric strength of nanofluid-impregnated transformer solid insulation

“…The improvement of the AC BDV of the NF used in this work is a 10 % according to previous works of the authors. [12].…”

“…The NFs were prepared in a two-step process by mixing the base MO with the Fe 3 O 4 dispersion to a concentration of NPs 0.2 g/L. This concentration value was chosen because in previous studies the NFs with that concentration of NPs showed the highest AC BDV values, while for higher concentrations the AC BDV of the liquid decreased [12].…”

“…An important number of experimental and theoretical works have been reported which support evidence that the addition of small concentrations of nanoparticles (NP) to insulating oils may have a beneficial effect on the behaviour of these fluids [8][9][10]. Enhancement of several oil properties that are relevant in transformer design have been reported, such as AC breakdown voltage [11][12][13][14], impulse breakdown voltage [15,16] and several thermal properties [17,18]. Although the use of these fluids for transformer insulation purposes is far from being feasible nowadays, it is believed that the observed improvements in the properties of insulating oils may lead to the construction of smaller and more efficient devices in the future [19].…”

Dielectric Response of the Oil-Paper Insulation System in Nanofluid-Based Transformers

“…Then, higher voltage levels are required to produce a breakdown [8], [11], [12], [13]. Another effect that has been observed is that the presence of NP increases the solubility of water in the base fluid, limiting the hazardous effect of the water on the breakdown voltage [14], [15].…”

Investigation of the Lightning Impulse Breakdown Voltage of Mineral Oil based Fe3O4 Nanofluids

“…In this work an exhaustive evaluation of the impulse breakdown voltage of several Fe 3 O 4 MO based NDF is carried out studying the differences between the streamer propagation in the MO and in the prepared NDF. The AC BDV of the same fluids was analyzed by the authors in a previous work [26,27]. Although the thermal properties of dielectric materials are important to describe the behavior of transformer insulation, this paper only handles the dielectric behavior of these materials when subjected to lightning impulse tests.…”