Challenge of mixed insulating liquids for use in high-voltage transformers.1. Investigation of mixed liquids

Fofana, I.; Wasserberg, V.; Borsi, H.; Gockenbach, E.

doi:10.1109/mei.2002.1014964

Cited by 178 publications

(69 citation statements)

References 9 publications

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“…However, the viscosity of natural esters is high, so an excessive content of natural esters will enhance the viscosity of the mixed oil. This conclusion is consistent with the results of Fofana et al [21], who also researched the electrical, physicochemical, and degradation properties of mixtures of mineral insulating oil with natural esters (olive oil) with different components. They found that hydrolysis of the natural esters increased the acid content of the mineral insulating oil and decreased the breakdown voltage of the mixed oil.…”

Section: Modification Of Non-nanoparticlessupporting

confidence: 92%

“…There are basically three states of moisture in insulating liquids, which are the dissolved state, emulsified state, and dispersed state. The moisture content in insulating oil can largely influence the electrical properties, that is, increase the electrical conductivity and dissipation factor and lower the electric strength of transformer oil [21].…”

Section: Breakdown Voltage Of Mineral Insulating Oilmentioning

confidence: 99%

“…Natural esters are considered an attractive green alternative to mineral insulating oil [1,87], and mixtures composed of natural esters and mineral insulating oil have become a research interest. In 2002, Fofana et al [21] studied the electrical and physicochemical properties of mixtures of natural esters and mineral insulating oil with different proportions. They found that when the natural ester content was less than 20%, all the electrical and physical properties of the mixtures were better than those of the traditional transformer mineral insulating oil.…”

Section: Modification Of Non-nanoparticlesmentioning

confidence: 99%

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Review of Research Progress on the Electrical Properties and Modification of Mineral Insulating Oils Used in Power Transformers

et al. 2018

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Abstract:In November 2017, the first ±1100 kV high-voltage direct-current power transformer in the world, which was made by Siemens in Nurnberg, passed its type test. Meanwhile, in early 2017, a ±1000 kV ultra-high voltage (UHV) substation was officially put into operation in Tianjin, China. These examples illustrate that the era of UHV power transmission is coming. With the rapid increase in power transmission voltage, the performance requirements for the insulation of power transformers are getting higher and higher. The traditional mineral oils used inside power transformers as insulating and cooling agents are thus facing a serious challenge to meet these requirements. In this review, the basic properties of traditional mineral insulating oil are first introduced. Then, the variation of electrical properties such as breakdown strength, permittivity, and conductivity during transformer operation and aging is summarized. Next, the modification of mineral insulating oil is investigated with a focus on the influence of nanoparticles on the electrical properties of nano-modified insulating oil. Recent studies on the performance of mineral oil at molecular and atomic levels by molecular dynamics simulations are then described. Finally, future research hotspots and notable research topics are discussed.

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Section: Modification Of Non-nanoparticlessupporting

confidence: 92%

Section: Breakdown Voltage Of Mineral Insulating Oilmentioning

confidence: 99%

Section: Modification Of Non-nanoparticlesmentioning

confidence: 99%

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Review of Research Progress on the Electrical Properties and Modification of Mineral Insulating Oils Used in Power Transformers

et al. 2018

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“…The relative moisture for oil is the dissolved moisture content of the oil relative to the maximum capacity of moisture that the oil can hold. The relative moisture W rel at a given temperature T is defined in terms of the actual moisture content in a liquid W abs versus the saturation limit W L (T) [25], as following:…”

Section: Moisture Content Of Oilsmentioning

confidence: 99%

A comparative study of physicochemical, dielectric and thermal properties of pressboard insulation impregnated with natural ester and mineral oil

Liao

Hao

Chen

et al. 2011

IEEE Trans. Dielect. Electr. Insul.

190

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Natural ester is considered to be a substitute of mineral oil in the future. To apply natural ester in large transformers safely, natural ester impregnated solid insulation should be proved to have comparable dielectric strength and thermal stability to mineral oil impregnated solid insulation. This paper mainly focuses on a comparative study of physicochemical, ac breakdown strength and thermal stability behavior of BIOTEMP natural ester/pressboard insulation and Karamay 25# naphthenic mineral oil/pressboard insulation after long term thermal ageing. The physicochemical and dielectric parameters including moisture, acids and the ac breakdown strength of these two oil/pressboard insulation systems at different ageing status were compared. The permittivity and ac breakdown strength of these two oil/pressboard insulation systems at different temperatures were also investigated. And a comparative result of the thermal stability behavior of these two oil/pressboard insulation systems with different ageing status was provided at last. Results show that though natural ester has higher absolute humidity and acidity during the long ageing period, the lower relative humidity of natural ester helps to keep its ac breakdown strength higher than mineral oil. The pressboard aged in natural ester also has higher ac breakdown strength than that aged in mineral oil. The lower relative permittivity ratio of natural ester impregnated paper to natural ester is beneficial to its dielectric strength. Using natural ester in transformer, the resistance to thermal decomposition of the oil/pressboard insulation system could be also effectively improved.Index Terms -Natural ester, mineral oil, pressboard, physicochemical, dielectric strength, thermal stability.

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Section: Thermal Ageing Experiments Of Oil-paper Insulation Samplesmentioning

confidence: 99%

Quantitative analysis ageing status of natural ester-paper insulation and mineral oil-paper insulation by polarization/depolarization current

Hao

Liao

Chen

et al. 2012

IEEE Trans. Dielect. Electr. Insul.

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Polarization and Depolarization Current (PDC) technique is an effective tool to assess the condition of oil-paper insulation system in power transformers. So far the PDC behaviors of mineral oil-paper insulation have been widely investigated. However, with the increasing number of transformer choosing natural ester as its insulation oil, it is important to investigate the PDC characteristics of natural ester-paper insulation to see whether the PDC technique can also be used to assess the condition of new insulation system using natural ester in transformers accurately. In this research, natural esterpaper insulation sample and mineral oil-paper insulation sample were subjected to thermally accelerated ageing experiment at 110 °C for 120 days. The PDC characteristics of natural ester-paper insulation sample and mineral oil-paper insulation sample were compared over the ageing process. A new method for assessing the ageing condition of the oil-paper insulation in terms of the depolarization charge quantity was proposed. Results show that the polarization/depolarization current of natural ester-paper insulation sample is higher than that of mineral oil-paper insulation sample with the same ageing intervals. The depolarization charge quantity of both kinds of oil-paper insulation sample is very sensitive to their ageing conditions. There is an exponential relation between the stable depolarization charge quantity of both kinds of oil-paper insulation sample and the degree of polymerization (DP) of paper. The depolarization charge quantity can be used to predict the ageing condition of oil-paper insulation providing the measurement temperature is kept the same.

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Challenge of mixed insulating liquids for use in high-voltage transformers.1. Investigation of mixed liquids

Abstract: Moisture is recognized to be "enemy number one" for transformer insulation.

Cited by 178 publications

References 9 publications

Review of Research Progress on the Electrical Properties and Modification of Mineral Insulating Oils Used in Power Transformers

Review of Research Progress on the Electrical Properties and Modification of Mineral Insulating Oils Used in Power Transformers

A comparative study of physicochemical, dielectric and thermal properties of pressboard insulation impregnated with natural ester and mineral oil

Quantitative analysis ageing status of natural ester-paper insulation and mineral oil-paper insulation by polarization/depolarization current

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