Fig 3 - uploaded by Konstantinos N. Koutras
Content may be subject to copyright.
LIV waveforms. (a) Withstand case (1.2/50 µs). (b) LI breakdown case waveform displaying the breakdown time.
Source publication
This study is focused on exploring the change in the dielectric and cooling efficiency of vegetable oil following the integration of semiconducting SiC and TiO2 nanoparticles in two different weight percentages by comparing the corresponding behavior of nanofluids at the time of their synthesis and after one month of ageing. The thermal response ha...
Contexts in source publication
Context 1
... applied LIV is measured through a capacitive voltage divider and monitored through Tektronix DPO4104; 1-GHz, 5-GS/s oscilloscope. A typical LIV signal recorded from the oscilloscope is presented in Fig. 3(a), while a corresponding LI BDV waveform displaying the BD time is depicted in Fig. 3(b). Thermal conductivity of as-prepared and one-month aged samples at temperature range from 25 • C to 90 • C. and computed from (3) for the range of the understudied temperature levels. The solid lines represent their response at the time of their ...
Context 2
... applied LIV is measured through a capacitive voltage divider and monitored through Tektronix DPO4104; 1-GHz, 5-GS/s oscilloscope. A typical LIV signal recorded from the oscilloscope is presented in Fig. 3(a), while a corresponding LI BDV waveform displaying the BD time is depicted in Fig. 3(b). Thermal conductivity of as-prepared and one-month aged samples at temperature range from 25 • C to 90 • C. and computed from (3) for the range of the understudied temperature levels. The solid lines represent their response at the time of their synthesis, while the dotted lines demonstrate the repeated measurements after one-month ...
Citations
... Researchers compared mineral oil-based nanofluids with low-concentration nanoparticles like Fe 3 O 4 , Al 2 O 3 , and TiO 2 . The majority of studies in this field have mainly concentrated on the thermal properties of internal insulating liquids [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. The study found that all nanofluids improved by at least 20% in AC breakdown voltage in the ideal concentration range of 0.1 g/L under AC circumstances [47]. ...
... The majority of studies in this field have mainly concentrated on the thermal properties of internal insulating liquids [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. The study found that all nanofluids improved by at least 20% in AC breakdown voltage in the ideal concentration range of 0.1 g/L under AC circumstances [47]. ...
With a focus on the development of sustainable alternate solutions for liquid insulation, this research focuses on the enhancement of biomass material. Emphasizing technical and sustainable challenges in traditional liquid insulation, the study addresses the pressing need for breakthroughs in dielectric liquid insulation. Motivated by the imperative for high-performing and sustainable insulating qualities, the research is dedicated to developing nanofluids by blending coconut kernel oil (CKO), palm kernel oil (PKO), and sunflower seed oil (SSO) with traditional transformer oil in a 70:30 ratio. To improve dielectric performance, oil samples undergo a systematic analysis with silica (SiO2), titania (TiO2), and zincite (ZnO) nanoparticles at varying mass fraction weights (0.04, 0.08, and 0.1 g/L). Findings reveal that higher nanoparticle concentrations lead to superior dielectric performance, especially in sunflower oil-infused nanofluids. These insights offer solutions for traditional liquid insulation challenges and deepen our understanding of interactions between vegetable oils and nanoparticle features. Methodical Taguchi and regression analyses are essential for comprehensively analyzing breakdown voltage characteristics across the samples. Data produced by these analyses is crucial for developing reliable prediction models, and establishing a robust foundation for effective and environmentally friendly dielectric liquid insulation systems, thus contributing significantly to the long-term progress of electrical insulation technology.
... The superior surge endurance demonstrated by the FR3-based nanofluid in comparison to mineral oil, coupled with the satisfactory dielectric performance of natural ester oil-based nanofluids 34 and their fire-resistant properties 17 , establishes a promising framework for the substitution of mineral oils with environmentally friendly liquids facilitated by nanotechnology processes in the forthcoming decades. This prospect, however, necessitates overcoming challenges related to the long-term stability of nanofluids, especially at high nanoparticle concentrations, and addressing aging effects resulting from oxidation and thermal stress 10,35,36 . Available synthesis methods and nanoparticles' dispersion techniques 21,22,37 will make feasible the stability of the surge-proof nanofluids; the shape, size, type, chemical treatment, and moisture content of liquids may be parameters that should be examined by the researchers towards this direction. ...
The surge endurance of natural ester oil-based nanofluids against surge events is investigated experimentally. The focus of this work is the examination, through dielectric spectroscopy measurements, of the alteration of the real and imaginary parts of the complex relative permittivity of iron oxide nanofluids as a result of an accelerated degradation test employing a sequence of repetitive current impulses produced via a 12 kV / 6 kA combination wave generator. The target is the exploration of a possible implementation of nanofluids as multipurpose liquids that act, in addition to insulation and coolants, as surge absorption media. Promising experimental results are discussed and compared with those of mineral oil that is widely used as a conventional insulating liquid in power transformers.
... Where ′ is the real part of the complex permittivity known as the dielectric constant and ′′ is the imaginary part of the complex permittivity known as the loss factor [170,176]. ...
... Notably, Fe 3 O 4 exhibited a superior modification effect compared to TiO 2 and Al 2 O 3 at the same content [34]. In the impact of integrating different weight percentages semiconducting SiC and TiO 2 nanoparticles into vegetable oil after 1 month of aging, assessing changes in dielectric properties and cooling efficiency revealed behavior of nanofluids that a worsening of properties with an increase in nanoparticle concentration, possibly attributed to quicker agglomeration [35,36]. The impact of concentration from 0.1 to 0.5 g/L is studied with employing highspeed agitation and ultrasonication for conducting (Fe 3 O 4 ), semi-conductive (ZnO), and insulating (ZrO 2 , SiO 2 , and Al 2 O 3 ) nanoparticles for analysis of AC dielectric strength of MIDEL 7131 synthetic ester (SE) and partial discharge activity. ...
This research addresses the pressing need for advancements in dielectric liquid insulation, recognizing the challenges associated with conventional liquid insulation. Motivated by the imperative to enhance dielectric performance, the study focuses on vegetable oil nanofluids, specifically sunflower oil (SFO), soybean oil (SBO), and rice bran oil (RBO), blended with conductive calamine (ZnO+Fe 2 O 3), insulative alumina (Al 2 O 3), and semiconductive tenorite (CuO) nanoparticles at 0.025% and 0.1% volume particle concentrations. The existing challenges in traditional liquid insulation include issues related to sustainability, efficiency, and the demand for improved dielectric properties in contemporary electrical systems. This research aims to address these challenges through a systematic investigation into the physicochemical properties of nanofluids and a statistical study on partial discharge inception voltage (PDIV) using normal and Weibull distributions. The outcomes of the study reveal that higher nanoparticle concentrations in nanofluids exhibit superior dielectric performance, with sunflower oil-based nanofluids enriched with calamine and tenorite nanoparticles surpassing those based on alumina. These findings not only contribute to a deeper understanding of the intricate relationships between nanoparticle characteristics and vegetable oil properties but also offer practical insights into overcoming challenges associated with conventional liquid insulation. This research is essential in paving the way for sustainable advancements in electrical insulation technology, providing a foundation for the development of efficient and environmentally friendly dielectric liquid insulation.
... In response to these issues, vegetable oil (VO) has been introduced as alternatives to MO, as they are an environmentally friendly renewable resource and have a high flash point. However, researchers seek to improve the heat transfer capabilities of these insulating fluids by adding NPs [9,10], The term NFs was introduced to improve the properties of fluids by researchers in 1995 [11]. It has been proven that NFs have great potential to improve the thermal conductivity of coolants used in transformers, thanks to the solid NPs which modify the properties of these insulating oils and thus absorb more heat in high voltage equipment, which reduces heat loss and improve transformer performance [12,13]. ...
The enhancement of the thermal conductivity of dielectric oils has a positive effect on the performance of electrical equipment that uses these oils as a cooling medium. Nanofluids (NFs) have inspired high-voltage engineers to use them as alternative fluids in power transformers due to their impressive heat transfer and insulation compared to traditional dielectric oils. The present study is a numerical simulation by COMSOL Multiphysics of the thermal conductivity of NFs based on dielectric oils used in power transformers, to identify the effect of temperature, the concentration of nanoparticles (NPs), type of insulating fluid and NPs on thermal conductivity. The NFs were modeled inside a cube using the finite element method (FEM) by applying a temperature gradient. Several types of NPs were used (SiC, ZnO, TiO2, and Al2O3) in addition to several volume concentrations (0%, 0.001%, 0.002%, 0.01%, and 0.02%). The results showed a significant improvement in the thermal conductivity of the NFs with increasing concentration since the best results were recorded at an estimated volume concentration of 0.02%, while the lowest results were obtained for samples using a volume concentration estimated at 0.001%. The base fluid (BF) type and NPs play a dominant role in the thermal performance of the NFs, as the vegetable oil-based nanofluid provided the highest thermal conductivity values and silicon carbides (SiC) was the best NPs used in this study. However, a decrease in thermal transfer capacities was observed for all samples with increasing temperature.
... In light of the promising results of recent studies on the dielectric withstand capability and thermal conductivity of nanofluids [13]- [15], active research in industry and academia is ongoing so as to come up with new insulating fluids and convincing theoretical interpretation of their improved performance [16]- [19]. On the other hand, there are concerns about the expected lifetime, long-term stability, and degradation of nanofluids in the field [20]- [22]. ...
The real part of the relative permittivity and the electrical conductivity of a natural ester oil, that serves as a liquid matrix for nanofluids, are measured for a wide frequency and electric field range. The focus of this work is the exploration of the modification of these basic electrical parameters of the liquid matrix after the integration of iron oxide nanoparticles. A series of experiments with the aid of an impedance analyzer, an LCR meter, and a variable-frequency power supply employing two different liquid test fixtures reveal an increase of both real and imaginary parts of relative permittivity with increasing nanoparticles concentration up to 0.5% w/w.
Natural ester oils are an environmentally friendly substitute for mineral oils that are commonly used as dielectric insulating liquid and coolant in power transformers. In this study, the real relative permittivity and DC breakdown voltage of a natural ester oil are experimentally examined. An accelerated degradation test employing 15 current impulses is employed to investigate the change of the basic electrical characteristics of the oil under study with the aid of a 1 MV/ 7 kJ Marx generator. Experimental results on the surge current withstand capability of the natural ester oil are presented and discussed.
