Reducing Environmental Impact and Improving Safety and Performance of Power Transformers With Natural Ester Dielectric Insulating Fluids

Asano, Roberto; Page, S. A.

doi:10.1109/tia.2013.2269532

Cited by 79 publications

(43 citation statements)

References 11 publications

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“…Government regulatory agents are imposing stiff penalties for spills of mineral oils in environments. There is a major environmental concern over the toxic effects of uncontained mineral oil spills [6]. Transformer oil is poorly biodegradable.…”

Section: Introductionmentioning

confidence: 99%

A review on critical evaluation of natural ester vis-a-vis mineral oil insulating liquid for use in transformers: Part 1

Mehta

Kundu

Chowdhury

et al. 2016

IEEE Trans. Dielect. Electr. Insul.

151

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In a long 130 years of its journey in service to mankind, the power transformer has grown in many aspects; ratings, performance, technology, aesthetics and ecofriendliness. Today, the transformer industry is witnessing the era of shifting from petroleum based mineral oils that are depleting, environmentally unfavorable, and proven dangerous to natural esters (vegetable oil based) that are renewable, environmentally friendly, and non-hazardous. The market and regulatory pressures to reduce liability risk exposure of mineral-oil-filled distribution and power transformers are increasing. In addition, there are demands to improve equipment efficiency and adopt more "earth-friendly" options in our power systems. In the last two decades there has been a resurgence of usage of natural ester insulating liquids for their "GREEN" and Safety credentials. These renewable resources have good dielectric properties and are compatible for use in power transformers. This paper evaluates and relates the new natural ester oil with existing mineral oil technology in terms of environmental concern, fire safety, physio-chemical properties, thermal performance, and dielectric performance. It also covers key modifications in design, manufacturing and operation to help assure excellent functionality and long life. In brief, this paper provides transformer designers and users about the advantages and challenges of "Green Insulating Liquid". Due to the voluminous properties that are compared and discussed, this paper is presented in two parts: Part 1 discusses on key properties and standards for the two liquids. Part 2 emphasizes on additional key properties and material compatibility related to electrical design. Based on evidence discussed in both parts, it is concluded that natural esters are acceptable for both new transformers and for retro filling existing units.

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Section: Introductionmentioning

confidence: 99%

A review on critical evaluation of natural ester vis-a-vis mineral oil insulating liquid for use in transformers: Part 1

Mehta

Kundu

Chowdhury

et al. 2016

IEEE Trans. Dielect. Electr. Insul.

151

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“…The sources of energy capable of splitting of a molecular covalent bond made up of a pair of electrons are three fold [1,9,16,17]:…”

Section: Background On Transformer Insulation's Agingmentioning

confidence: 99%

“…Note that two measurements have been performed on days 8,9, and 15 at 6 h intervals. This data is listed in Table 2.…”

Section: Repeatabilitymentioning

confidence: 99%

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Measurement of the Relative Free Radical Content of Insulating Oils of Petroleum Origin

Fofana

Sabau²,

Bétié

2015

Energies

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Oil/paper insulation degradation in transformers involves chemical and physical changes in the materials. Some of the chemical reactions involve very reactive intermediates called free radicals. Free radicals play a major role in a wide variety of ageing processes. The detection of these reactive species in oil may, in principle, provide useful information for monitoring oil degradation. This manuscript details a laboratory technique, which determines the relative content of free radicals in insulating oils of petroleum origin by a spectrophotometric method. Free radicals may be formed in oils under operating or test conditions. The procedure enables the determination of the relative concentration of free radicals, which can act as the precursors of decay products such as charge carriers, oxidized molecules, as well as polymerization products. The technique involves using a reactive free radical reagent, 2,2-diphenyl-1-picrylhydrazyl (DPPH), added to oil to assess free radical concentration. This method is applicable to new, reclaimed, or used oils as well as naturally or artificially oxidized oil (the cause of aging can be chemical, physical, or electrical). In this contribution, free radicals were assessed following electrical discharge application in oil.

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“…With the development of the transformer industry, the concerns of environmental impacts have become more and more important. To answer these concerns, the ester liquids have become a promising alternative of the conventional mineral oil due to its higher fire point and lower environmental impact [18]. With the increasing application of ester liquids in large power transformers, it is essential to have a comprehensive understanding of its dielectric behaviors including PD and streamer characteristics at different temperatures.…”

Section: Introductionmentioning

confidence: 99%

Effects of temperature on partial discharges and streamers in an ester liquid under AC stress

Huang

Liu

Wang

2019

IEEE Trans. Dielect. Electr. Insul.

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Insulating liquids in transformers experience the transformer operational temperature rather than the ambient temperature that is often used in discharge studies in laboratories. This paper presents the effects of temperature on partial discharge (PD) and streamer characteristics of a synthetic ester liquid under AC stress. A needle-toplane electrode configuration was employed to perform the PD and streamer measurements. The PD pattern, streamer images, current signals were chosen to explore the PD and streamer characteristics at temperatures of 20, 40, 60 and 80 ºC. It was found that both PD and streamer characteristics of the synthetic ester are temperature dependent. As the temperature increased, the magnitude and repetition rate of positive PDs increased slightly, but both the magnitude and repetition rate of negative PDs dropped dramatically. In addition, it was observed that when the temperature increased, the stopping length of positive streamers did not change appreciably while a significant reduction of negative streamer length and area was witnessed. A mechanism based on the electrohydrodynamics (EHD) phenomenon and the space charge theory has been used to explain the different effects of temperature on positive and negative PDs.

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Reducing Environmental Impact and Improving Safety and Performance of Power Transformers With Natural Ester Dielectric Insulating Fluids

Cited by 79 publications

References 11 publications

A review on critical evaluation of natural ester vis-a-vis mineral oil insulating liquid for use in transformers: Part 1

A review on critical evaluation of natural ester vis-a-vis mineral oil insulating liquid for use in transformers: Part 1

Measurement of the Relative Free Radical Content of Insulating Oils of Petroleum Origin

Effects of temperature on partial discharges and streamers in an ester liquid under AC stress

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