Analysis of incipient discharge activity in nano particles dispersed ester oil insulation
01 Sep 2017-pp 563-566
TL;DR: In this article, Fourier Transform Infrared spectroscopy (FTIR) analysis was carried out in order to quantify effect of nano particles on surface characteristics of oil impregnated pressboard (OIP) sample.
Abstract: In recent times, ester oil is used as insulation in transformers. In order to improve the performance characteristics, silicondioxide nano particles were dispersed in the oil. An attempt has been made to understand the corona activity under high frequency AC and harmonic AC voltages with different level of distortion. No characteristic variation in corona inception voltage is observed with increase in supply voltage frequency. The UHF signal formed during corona discharge activity has dominant frequency at near 1 GHz An attempt has been made to understand the surface charge accumulation characteristics of paper insulation impregnated in nano particle dispersed ester oil. It is observed that in paper insulation in nano ester oil, the initial charge accumulation is low. Phase resolved PD analysis was carried out to understand corona activity in ester oil and nano particle dispersed ester oil, under AC and harmonic AC voltages. Fourier Transform Infrared spectroscopy (FTIR) analysis was carried out in order to quantify effect of nano particles on surface characteristics of oil impregnated pressboard (OIP) sample.
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01 Sep 2018
TL;DR: In this article, the effect of SiO 2 on dielectric properties of natural ester oil has been studied based on various electrical analysis, an attempt has been made to identify the optimum concentration of nanoparticles in terms of volume concentration.
Abstract: Ester Oil has been most commonly suggested as an alternative transformer oil insulation owing to its higher biodegradability and excellent dielectric and thermal properties. Development of nanofluids based on ester oil is considered as the future of insulating fluids which hold great potential to enhance the design aspect of high voltage apparatus. In the current study effect of SiO 2 on dielectric properties of natural ester oil has been studied. Based on various electrical analysis, an attempt has been made to identify the optimum concentration of nanoparticles in terms of volume concentration. In order to enhance dispersion and improve surface properties, CTAB has been chosen as a surfactant and its optimum concentration with respect to nanofluid has been established. Corona Inception Voltage (CIV) results indicate that beyond a certain value, addition of nanoparticles can degrade the dielectric properties of oil. These results are further confirmed by testing the Levitation Voltage of the particle in the electrode gap. It is realized that incipient discharges due to corona/particle movement can radiate electro-magnetic waves with its frequency lying in Ultra High Frequency (UHF) signal range. It is observed that the bandwidth of the radiated signal lies in the frequency range of 0.7-2 GHz, with its dominant frequency at 0.9 GHz. It was observed that the number of discharges caused due to corona/particle movement are less for the identified optimum concentration of nano SiO 2 in transformer oil. It has been observed that the number of discharges is higher for AC voltage than DC voltage, due to particle movement.
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Cites background from "Analysis of incipient discharge act..."
...It has been previously reported that addition of surfactant not just help stabilize the dispersion level of the nanoparticle but also improve its dielectric strength [12]....
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References
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TL;DR: The role of electrical insulation is critical for the proper operation of electrical equipment and it is therefore essential to dissipate the heat generated by the energy losses, especially under high load conditions.
Abstract: The role of electrical insulation is critical for the proper operation of electrical equipment. Power equipment cannot operate without energy losses, which lead to rises in temperature. It is therefore essential to dissipate the heat generated by the energy losses, especially under high load conditions. Failing to do so results in premature aging, and ultimately to failure of the equipment. Heat dissipation can be achieved by circulating certain liquids, which also ensure electrical insulation of energized conductors. The insulating-fluids market is therefore likely to be dominated by liquids, leaving to gases (such as compressed air and SF6) limited applications in power equipment such as circuit breakers and switchgear [1]-[3]. Several billion liters of insulating liquids are used worldwide in power equipment such as transformers (power, rectifier, distribution, traction, furnace, potential, current) [4], resistors [5], reactors [6], capacitors [7], cables [8], bushings [9], circuit breakers [10], tap changers [11], thyristor cooling in power electronics, etc. [12]. In addition to their main functions of protecting solid insulation, quenching arc discharges, and dissipating heat, insulating liquids can also act as acoustic dampening media in power equipment such as transformers. More importantly, they provide a convenient means of routine evaluation of the condition of electrical equipment over its service life. Indeed, liquids play a vital role in maintaining the equipment in good condition (like blood in the human body). In particular they are responsible for the functional serviceability of the dielectric (insulation) system, the condition of which can be a decisive factor in determining the life span of the equipment [13]. Testing the physicochemical and electrical properties of the liquids can provide information on incipient electrical and mechanical failures. In some equipment, liquid samples can be obtained without service interruption.
284 citations
"Analysis of incipient discharge act..." refers background in this paper
...Conventionally, mineral oil is used for insulation of transformers [2]....
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Book•
06 Sep 2012
TL;DR: Transformer Engineering: Design, Technology, and Diagnostics, Second Edition as discussed by the authors helps to design better transformers, apply advanced numerical field computations more effectively, and tackle operational and maintenance issues.
Abstract: Transformer Engineering: Design, Technology, and Diagnostics, Second Edition helps you design better transformers, apply advanced numerical field computations more effectively, and tackle operational and maintenance issues. Building on the bestselling Transformer Engineering: Design and Practice, this greatly expanded second edition also emphasizes diagnostic aspects and transformer-system interactions.
What’s New in This Edition
Three new chapters on electromagnetic fields in transformers, transformer-system interactions and modeling, and monitoring and diagnostics
An extensively revised chapter on recent trends in transformer technology
An extensively updated chapter on short-circuit strength, including failure mechanisms and safety factors
A step-by-step procedure for designing a transformer
Updates throughout, reflecting advances in the field
A blend of theory and practice, this comprehensive book examines aspects of transformer engineering, from design to diagnostics. It thoroughly explains electromagnetic fields and the finite element method to help you solve practical problems related to transformers. Coverage includes important design challenges, such as eddy and stray loss evaluation and control, transient response, short-circuit withstand and strength, and insulation design. The authors also give pointers for further research. Students and engineers starting their careers will appreciate the sample design of a typical power transformer.
Presenting in-depth explanations, modern computational techniques, and emerging trends, this is a valuable reference for those working in the transformer industry, as well as for students and researchers. It offers guidance in optimizing and enhancing transformer design, manufacturing, and condition monitoring to meet the challenges of a highly competitive market.
142 citations
"Analysis of incipient discharge act..." refers background in this paper
...Oil-insulated highvoltage equipment, such as power transformers and converter transformers are one of the most vital components of power system [1]....
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Journal Article•
95 citations
"Analysis of incipient discharge act..." refers background in this paper
...Surfactant helps avoid agglomeration of nano particles at a particular location and ensures uniformity of dispersion [8]....
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TL;DR: In this article, three different insulating liquids, natural ester, mineral oil which is currently used by the Public Power Corporation of Greece and a nanofluid of surface coated Fe3O4 nanoparticles, were subjected to AC voltage stress and their statistical breakdown voltage was measured and compared.
Abstract: In this study, three different insulating liquids, natural ester, mineral oil which is currently used by the Public Power Corporation of Greece and a nanofluid of surface coated Fe3O4 nanoparticles into a natural ester matrix, were subjected to AC voltage stress and their statistical breakdown voltage was measured and compared. Three different electrode configurations were used during the measurements in order to study the effect of non-uniform fields on the breakdown voltage distribution. Four different statistical distributions were used for the statistical processing of the experimental results. The two of them were the frequently used normal and Weibull distributions; in addition, Gumbel and generalised extreme value (GEV) function distributions were studied. It was shown that, in most cases, the experimental data followed GEV and Weibull functions rather than normal or Gumbel. Therefore, GEV statistics fits indiscriminately better to the experimental results concerning breakdown voltage, for the three different electrodes configuration and the three understudied insulating oils. The experimental results indicated that nanofluid has better performance, in terms of dielectric breakdown voltage, compared with natural ester oil and mineral oil, hence nanofluid is considered as a potential substitute of the conventional dielectric liquids, with enhanced properties and prospects.
84 citations
TL;DR: In this paper, an analysis of the power developed due to dielectric heating in two different materials subjected to voltage waveforms with high harmonic content is presented, by expressing the non-sinusoidal loss as an enhancement factor to the sinusoidal one, a geometryindependent formalism is derived.
Abstract: Dielectric heating is one potential aging mechanism active below partial discharge inception voltage in materials used as high voltage insulation. When exposed to voltage waveforms containing high amount of harmonics, the heat generation will be larger due to increased power losses as compared with power frequency excitation. This may result in a decreased life or even failure of insulation due to the increased operating temperature or to thermal runaway. An analysis of the power developed due to dielectric heating in two different materials subjected to voltage waveforms with high harmonic content is presented in this paper. By expressing the non-sinusoidal loss as an enhancement factor to the sinusoidal one, a geometry-independent formalism is derived. From dielectric response measurements at low voltage and at several temperatures the dielectric power loss in the material can be calculated for different voltage levels and waveforms. Two important material parameters can be extracted from the calculated dielectric power loss: (i) non-sinusoidal loss compared with sinusoidal loss with the same fundamental frequency (pfact) and (ii) change of loss with changing temperature (dpfact/dT). These two parameters could potentially be used to indicate the suitability of materials for use in applications where voltage waveforms contain high harmonic content.
80 citations