Abstract

Nowadays, studies of alternative liquid insulation in high voltage apparatus have become increasingly important due to higher concerns regarding safety, sustainable resources and environmentally friendly issues. To fulfil this demand, natural ester has been extensively studied and it can become a potential product to replace mineral oil in power transformers. In addition, the incorporation of nanoparticles has been remarkable in producing improved characteristics of insulating oil. Although much extensive research has been carried out, there is no general agreement on the influence on the dielectric response of base oil due to the addition of different amounts and conductivity types of nanoparticle concentrations. Therefore, in this work, a natural ester-based nanofluid was prepared by a two-step method using iron oxide (Fe2O3) and titanium dioxide (TiO2) as the conductive and semi-conductive nanoparticles, respectively. The concentration amount of each nanoparticle types was varied at 0.01, 0.1 and 1.0 g/L. The nanofluid samples were characterised by visual inspection, morphology and the dynamic light scattering (DLS) method before the dielectric response measurement was carried out for frequency-dependent spectroscopy (FDS), current-voltage (I-V), and dielectric breakdown (BD) strength. The results show that the dielectric spectra and I-V curves of nanofluid-based iron oxide increases with the increase of iron oxide nanoparticle loading, while for titanium dioxide, it exhibits a decreasing response. The dielectric BD strength is enhanced for both types of nanoparticles at 0.01 g/L concentration. However, the increasing amount of nanoparticles at 0.1 and 1.0 g/L led to a contrary dielectric BD response. Thus, the results indicate that the augmentation of conductive nanoparticles in the suspension can lead to overlapping mechanisms. Consequently, this reduces the BD strength compared to pristine materials during electron injection in high electric fields.

Highlights

  • Mineral-based insulation oil has been widely used in oil-immersed power transformers

  • The key success of mineral oil is mainly due to its dual functionality as a good dielectric material with cooling abilities and thee low cost associated with its availability

  • The results show that titanium dioxide is more promising as a nanoparticle in natural ester for insulation purposes

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Summary

Introduction

Mineral-based insulation oil has been widely used in oil-immersed power transformers. The key success of mineral oil is mainly due to its dual functionality as a good dielectric material with cooling abilities and thee low cost associated with its availability. The expansion of urbanisation processes has led to ultra-high power demands and is pushing power networks to their limits. The failure rate of large power transformers increases, resulting in major environmental. Energies 2018, 11, 333 damage and safety concerns. Mineral-oil-based transformer explosions can cause toxicity from the methane gas and oil spill onto the ground [1]. Greater safety concerns have resulted in the search for an alternative insulation oil.

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