scholarly journals Lightning Impulse Withstand of Natural Ester Liquid

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1964 ◽  
Author(s):  
Stephanie Haegele ◽  
Farzaneh Vahidi ◽  
Stefan Tenbohlen ◽  
Kevin Rapp ◽  
Alan Sbravati
Keyword(s):  
Breakdown Voltage ◽  
Dielectric Strength ◽  
Mineral Oil ◽  
Homogeneous Field ◽  
Inhomogeneous Field ◽  
Insulating Liquids ◽  
Lightning Impulse ◽  
Insulating Liquid ◽  
Natural Ester ◽  
Inhomogeneity Factor

Due to the low biodegradability of mineral oil, intense research is conducted to define alternative liquids with comparable dielectric properties. Natural ester liquids are an alternative in focus; they are used increasingly as insulating liquid in distribution and power transformers. The main advantages of natural ester liquids compared to mineral oil are their good biodegradability and mainly high flash and fire points providing better fire safety. The dielectric strength of natural ester liquids is comparable to conventional mineral oil for homogeneous field arrangements. However, many studies showed a reduced dielectric strength for highly inhomogeneous field arrangements. This study investigates at which degree of inhomogeneity differences in breakdown voltage between the two insulating liquids occur. Investigations use lightning impulses with different electrode arrangements representing different field inhomogeneity factors and different gap distances. To ensure comparisons with existing transformer geometries, investigations are application-oriented using a transformer conductor model, which is compared to other studies. Results show significant differences in breakdown voltage from an inhomogeneity factor of 0.1 (highly inhomogeneous field) depending on the gap distance. Larger electrode gaps provide a larger inhomogeneity at which differences in breakdown voltages occur.

scholarly journals Electrostatic Charging Tendency Analysis Concerning Retrofilling Power Transformers with Envirotemp FR3 Natural Ester

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4420 ◽  
Author(s):  
Maciej Zdanowski
Keyword(s):  
Mineral Oil ◽  
Volume Density ◽  
Point Of View ◽  
Pipe Material ◽  
Mineral Oils ◽  
Insulating Liquids ◽  
Electrostatic Charging ◽  
Tendency Analysis ◽  
Insulating Liquid ◽  
Natural Ester

Natural and synthetic esters are liquids characterized by insulating properties, high flash point, and biodegradability. For this reason, they are more and more often used as an alternative to conventional mineral oils. Esters are used to fill new or operating transformers previously filled with mineral oil (retrofilling). It is technically unfeasible to completely remove mineral oil from a transformer. Its small residues create with esters a mixture with features significantly different from those of the base liquids. This article presents electrostatic charging tendency (ECT) tests for mixtures of fresh and aged Trafo EN mineral oil with Envirotemp FR3 natural ester from the retrofilling point of view. Under unfavorable conditions, the flow electrification phenomenon can damage the solid insulation in transformers with forced oil circulation. The ECT of the insulating liquids has been specified using the volume density of the qw charge. This parameter has been determined using the Abedian–Sonin model on the basis of the electrification current measured in the flow system, as well as selected physicochemical properties of the liquids. It was shown that ECT is strongly dependent on the type of insulating liquid and pipe material, as well as the composition of the mixtures. The most important finding from the research is that a small amount (up to 10%) of fresh and aged mineral oil is effective in reducing the ECT of Envirotemp FR3 natural ester.

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

Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 799 ◽  
Author(s):  
Víctor A. Primo ◽  
Belén García ◽  
Juan Carlos Burgos ◽  
Daniel Pérez-Rosa
Keyword(s):  
Dielectric Properties ◽  
Breakdown Voltage ◽  
Mineral Oil ◽  
Power Transformers ◽  
Experimental Conditions ◽  
Insulating Materials ◽  
Recent Interest ◽  
Insulating Liquids ◽  
Lightning Impulse ◽  
Transformer Design

The recent interest in the development of nanomaterials has led researchers to the study of their electrical properties and the applications that they may have as insulating materials. One of these applications is the use of nanofluids as electrical insulation of power transformers. It has been reported that the dielectric properties of insulating liquids in which small amounts of nanoparticles have been dispersed are, in some cases, superior to those of the base fluids. Although these materials are promising, and their application could lead to advantages for the transformer design and reliability in the future, more research is necessary to evaluate different combination of materials under a wider range of experimental conditions. In this paper, a research on the lightning impulse breakdown voltage of mineral oil and several Fe3O4-based nanofluids is presented. Fluids prepared with different concentrations of nanoparticles were subjected to impulse lightning voltages considering both positive and negative polarities. As shown in this work the positive impulse breakdown voltage of the liquids showed improvements of up to 50%; in the case of the negative impulses not significant improvements were obtained.

scholarly journals Influence of Molecule Structure on Lightning Impulse Breakdown of Ester Liquids

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1061
Author(s):  
Huaqiang Li ◽  
Linfeng Xia ◽  
Shengwei Cai ◽  
Zhiqiang Huang ◽  
Jiaqi Li ◽  
...  
Keyword(s):  
Electric Fields ◽  
Breakdown Voltage ◽  
Experimental Research ◽  
Environmentally Friendly ◽  
Mineral Oil ◽  
Positive Polarity ◽  
Mineral Oils ◽  
Synthetic Ester ◽  
Lightning Impulse ◽  
Natural Ester

Ester liquids are environmentally friendly insulating oils, and they can be used as an alternative to mineral oil in transformers, even though in most countries spills of ester oils must be treated like spills of mineral oil. Furthermore, the breakdown characteristics of ester liquids are worse than those of mineral oils in heterogeneous electric fields. In this paper, we present a comprehensive experimental research on both positive and negative lightning impulse breakdown properties in point-plane geometries with gaps varying from 1 mm to 50 mm. The breakdown voltages and streamer velocities of five kinds of ester liquids, including natural ester, synthetic ester, and three kinds of single component esters have been measured. The results show that the double bonds have no effect on the breakdown voltage of ester liquids. The average streamer velocities of mono-esters are faster than that of other esters under positive polarity, and the breakdown voltages of all esters are close.

Effect of Water on Electrical Properties of Refined, Bleached, and Deodorized Palm Oil (RBDPO) as Electrical Insulating Material

2013 ◽  
Vol 64 (4) ◽  
Author(s):  
Nazera Ismail ◽  
Yanuar Z. Arief ◽  
Zuraimy Adzis ◽  
Shakira A. Azli ◽  
Abdul Azim A. Jamil ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Breakdown Voltage ◽  
Palm Oil ◽  
Pour Point ◽  
Electrical Breakdown ◽  
Dissipation Factor ◽  
Mineral Oil ◽  
Flash Point ◽  
Effect Of Water ◽  
Insulating Liquid

This paper describes the properties of refined, bleached, deodorized palm oil (RBDPO) as having the potential to be used as insulating liquid. There are several important properties such as electrical breakdown, dielectric dissipation factor, specific gravity, flash point, viscosity and pour point of RBDPO that was measured and compared to commercial mineral oil which is largely in current use as insulating liquid in power transformers. Experimental results of the electrical properties revealed that the average breakdown voltage of the RBDPO sample, without the addition of water at room temperature, is 13.368 kV. The result also revealed that due to effect of water, the breakdown voltage is lower than that of commercial mineral oil (Hyrax). However, the flash point and the pour point of RBDPO is very high compared to mineral oil thus giving it advantageous possibility to be used safely as insulating liquid. The results showed that RBDPO is greatly influenced by water, causing the breakdown voltage to decrease and the dissipation factor to increase; this is attributable to the high amounts of dissolved water.

scholarly journals Effect of electrical discharge on the properties of natural esters insulating fluids

2021 ◽  
Vol 23 (3) ◽  
pp. 1281
Author(s):  
Imran Sutan Chairul ◽  
Sharin Ab Ghani ◽  
Nur Hakimah Ab Aziz ◽  
Mohd Shahril Ahmad Khiar ◽  
Muhammad Syahrani Johal ◽  
...  
Keyword(s):  
Water Content ◽  
Breakdown Voltage ◽  
Electrical Discharge ◽  
Mineral Oil ◽  
Electrical Discharges ◽  
Inhomogeneous Electric Field ◽  
Sustainable Resources ◽  
Low Viscosity ◽  
Environmental Friendly ◽  
Natural Ester

<p>Vegetable oils have been an alternative to mineral oil for oil-immersed transformers due to concern on less flammable, environmental-friendly, biodegradable, and sustainable resources of petroleum-based insulating oil. This paper presents the effect of electrical discharges (200 up to 1000 discharges) under 50 Hz inhomogeneous electric field on the properties (acidity, water content, and breakdown voltage) of two varieties of vegetable based insulating oils; i) natural ester (NE) and ii) low viscosity insulating fluids derived from a natural ester (NE<sub>LV</sub>). Results show the water content, acidity and breakdown voltage of NE fluctuate due to applied discharges, while NE<sub>LV</sub> display insignificant changes. Hence, results indicate that the low viscosity insulating fluids derived from natural ester tend to maintain their properties compared to natural ester.</p>

scholarly journals The Impact of TiO2 Nanoparticle Concentration Levels on Impulse Breakdown Performance of Mineral Oil-Based Nanofluids

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 627 ◽  
Author(s):  
Ziyi Wang ◽  
You Zhou ◽  
Wu Lu ◽  
Neng Peng ◽  
Weijie Chen
Keyword(s):  
Tio2 Nanoparticles ◽  
Electric Fields ◽  
Breakdown Voltage ◽  
Concentration Level ◽  
Breakdown Strength ◽  
Mineral Oil ◽  
Interfacial Region ◽  
Bulk Oil ◽  
Lightning Impulse ◽  
The Impact

The insulation of mineral oil-based nanofluids was found to vary with different concentration level of nanoparticles. However, the mechanisms behind this research finding are not well studied. In this paper, mineral oil-based nanofluids were prepared by suspending TiO2 nanoparticles with weight percentages ranging from 0.0057% to 0.0681%. The breakdown voltage and chop time of nanofluids were observed under standard lightning impulse waveform. The experimental results show that the presence of TiO2 nanoparticles increases the breakdown voltage of mineral oil under positive polarity. The enhancement of breakdown strength tends to saturate when the concentration of nanoparticle exceeds 0.0227 wt%. Electronic traps formed at the interfacial region of nanoparticles, which could capture fast electrons in bulk oil and reduce the net density of space charge in front of prebreakdown streamers, are responsible for the breakdown strength enhancement. When the particle concentration level is higher, the overlap of Gouy–Chapman diffusion layers results in the saturation of trap density in nanofluids. Consequently, the breakdown strength of nanofluids is saturated. Under negative polarity, the electrons are likely to be scattered by the nanoparticles on the way towards the anode, resulting in enhanced electric fields near the streamer tip and the decrement of breakdown voltage.

scholarly journals Streamer propagation in a non-uniform electric field under lightning impulse in short gaps insulated with natural ester and mineral oil

2016 ◽  
Vol 64 (1) ◽  
pp. 171-179 ◽  
Author(s):  
P. Rozga
Keyword(s):  
Light Emission ◽  
Experimental Studies ◽  
Mineral Oil ◽  
Uniform Electric Field ◽  
Light Pulses ◽  
Streamer Propagation ◽  
Lightning Impulse ◽  
Small Electrode ◽  
Acceleration Voltage ◽  
Natural Ester

Abstract This article describes the comparative experimental studies on streamer propagation in natural ester and mineral oil under a high voltage lightning impulse. These studies were concentrated around the small electrode gaps and the point-plane electrode arrangement. The spatial shapes of the developing streamers, light emission and propagation velocity were analyzed and compared between the two different dielectric liquids. In both of them two streamer propagation modes were registered during the studies performed. Propagation of slow 2nd mode streamers took place below the so-called acceleration voltage while fast 3rd mode streamers developed at acceleration voltage and above. Comparing the streamer shapes corresponding to a given voltage polarity, no visible differences were observed between the liquids tested. Concerning the light emission, higher frequencies of light pulses were registered however in the case of natural ester. The significant differences between both liquids were noticed in the value of the acceleration voltage estimated. In the case of positive polarity streamers started to develop in natural ester as a 3rd mode at lower value of testing voltage than in the case of mineral oil. For negative polarity, within the applied testing voltages, 3rd mode streamers appeared only in natural ester. On this basis, the fundamental conclusion is that natural ester may have a lower ability of preventing the development of fast and energetic 3rd mode streamers, even at small electrode gaps.

Fillers in Electrical Papers for Power Transformers

2014 ◽  
Vol 875-877 ◽  
pp. 335-340 ◽  
Author(s):  
Primo Alberto Calva ◽  
Aarón Israel Díaz ◽  
Hugo Martínez Gutierrez
Keyword(s):  
Electrical Properties ◽  
Theoretical Analysis ◽  
Structural Parameters ◽  
Dielectric Strength ◽  
Mineral Oil ◽  
Dielectric Behavior ◽  
Power Transformers ◽  
Mechanical Resistance ◽  
Kraft Paper ◽  
Natural Ester

The electric papers have a wide variety of uses like in transformers, cables and power capacitors. Each application involves different requirements related to its mechanical and electric properties. The kraft is the dielectric paper most used due its high mechanical resistance and a dielectric strength of around 5 kV/mm that is increased up to 30 kV/mm when is impregnated with mineral oil and typically has a density of 0.7, nevertheless continuous improvements in the design, for example, of power transformers raise the need to improve its electrical properties particularly those related to its relative permittivity. In this article, structural parameters such as distribution and pore size of kraft paper and theoretical analysis for possible addition of nanofillers to improve their dielectric behavior are reported. A possible and better criterion for designing transformers can be the employment of kraft paper nano-inserted with 5 % of TiO2 or BaTiO3 stew in mineral oil and immersed in natural ester liquid.

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