Streamer characteristic and breakdown in a mineral oil and a synthetic ester liquid under DC voltage

Xiang, Jing; Liu, Q.; Wang, Zhongdong

doi:10.1109/tdei.2018.006938

Cited by 18 publications

(5 citation statements)

References 19 publications

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“…With an increase in propagation velocity, streamers' shape and light also change. The spatial shapes and oscillography of streamers have been investigated and analyzed in accordance with propagation velocities, electrode gaps, and acceleration voltages in mineral oil and synthetic esters [73], [74]. Synthetic esters were found to be inferior to mineral oils in resisting the growth of a streamer.…”

Section: Pre-breakdown Phenomenamentioning

confidence: 99%

Alternative Dielectric Fluids for Transformer Insulation System: Progress, Challenges, and Future Prospects

et al. 2019

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Ester-based dielectric fluids have gained widespread popularity for applications in high voltage apparatus. Synthetic and natural esters have been subjected to research for decades vis-à-vis mineral insulating oils around the world. Although many researchers favor the application of ester fluids, utilities are still uncertain and application of these alternatives remains a challenge. The intent of this survey is to present recent research progress and highlight the state of the art of key aspects that should be emphasized in future research. The contemporary research scenarios pertaining to the performance of ester fluids versus mineral oils, miscibility, and retrofilling of insulating fluids are discussed. In addition, pre-breakdown phenomena, usage of esters in on-load tap changers, environmental and fire resistance properties, and use of esters in cold climates are also discussed. Importantly, challenges and future aspects that should be investigated to improve the existing knowledge of ester dielectric fluids for applications in transformer technology are highlighted.

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Section: Pre-breakdown Phenomenamentioning

confidence: 99%

Alternative Dielectric Fluids for Transformer Insulation System: Progress, Challenges, and Future Prospects

et al. 2019

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“…However, a synthetic ester is comparable quantitively with mineral oil. Xiang et al [76] reported totally different conclusions concerning the DC-BDV. These conclusions were based on measurements in a point-to-sphere electrode arrangement representing non-uniform electrical field distributions.…”

Section: Ac and DC Breakdown Voltagementioning

confidence: 99%

“…However, the obtained results in each case exceed 60 kV, which is enough of a value for the dielectric liquids to be applied in devices of nominal voltages equal to 69 kV or higher. The available data are limited in the case of DC stress-based tests of synthetic esters [75][76][77]. In [75,77] the authors compared simply the DC-BDV between selected types of dielectric liquids and their mixtures in a quasi-uniform electric field created by a sphere-to-sphere electrode system.…”

Section: Ac and DC Breakdown Voltagementioning

confidence: 99%

A Review on Synthetic Ester Liquids for Transformer Applications

et al. 2020

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Synthetic esters have become more and more popular in last few decades, explaining the increasing number of units filled with this liquid year by year. They have been investigated under different aspects, both from the fundamental point of view and breakdown mechanisms, well as from the application point of view. However, their use in high voltage equipment is always a challenge and deeper knowledge of the various aspects that can be encountered in their exploitation is needed. The intent of this review paper is to present the recent research progress on synthetic ester liquid in relation to the selected issues, most important for ester development in the authors’ opinion. The described issues are the breakdown performance of synthetic esters, lightning impulse strength and pre-breakdown phenomena of synthetic esters, synthetic esters-based nanofluids, combined paper-synthetic ester based insulating systems, application of synthetic ester for retro-filling and drying of mineral oil-immersed transformers, DGA(dissolved gas analysis)-based diagnosis of synthetic esters filled transformers as well as static electrification of synthetic esters. The different sections are based both on the data available in the literature, but above all on the authors’ own experience from their research work on synthetic ester liquids for electrical application purposes.

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“…Most previous investigations focused on conductivity caused by oil contamination. Other researchers investigated the influence of LI on streamer characteristics (with and without pressboard interface) or the breakdown and withstand voltage of various insulating oils in a field [23]. One study examined the effects of electrodes, impulse shape, nature of dielectric liquid and cellulose particles [24].…”

Section: Introductionmentioning

confidence: 99%

Breakdown Voltage of Transformer Oil Containing Cellulose Particle Contamination With and Without Bridge Formation Under Lightning Impulse Stress

et al. 2021

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This study investigates the effect of cellulose bridge formation on insulating oil. Such effect influences the breakdown voltage and strength of mineral oil (MO) under standard lightning impulse (LI) voltage. A cylindrical test vessel fitted with spherical-spherical electrodes with a 2 mm gap distance between them was used to generate a quasi-uniform field and observe bridge formation between the gaps. A positive LI waveform (1.2/50 µs) generated by an impulse generator was applied during the breakdown tests. The rising-voltage method was used to measure the breakdown voltage in accordance with the International Electrotechnical Commission 60897 standard test method. Weibull cumulative breakdown probability was applied to present the breakdown results statistically, and the outcome was compared with clean oil (CO). Commercial cellulose microcrystalline particles were dispersed into the transformer oil to act as bridge. The concentrations of the samples were 0.004%, 0.008% and 0.012% by weight. The breakdown test results showed that the cellulosic particles reduced the LI breakdown voltage (LIBV) of MO by up to 10%. The influence of cellulose particles on LIBV was also more prominent during bridge formation, with a further reduction of 14%. Evidently, the presence of the cellulose bridge exerted a detrimental effect on the breakdown voltage of MO under LI stress, yielding a reduction of 24% and 27% at 0.004 wt% and 0.012 wt%, respectively. Finite element analysis also indicated that the electrical field strength of cellulosic particle contamination of 0.004 wt% and 0.012 wt% without a bridge skeleton exceeded the critical electric field strength of CO by 20% and 61%, respectively. In conclusion, the presence of cellulosic contamination at any concentration, i.e. either with or without a bridge structure, clearly decreased the breakdown voltage and strength of transformer oil. However, breakdown may not develop immediately because the bridge at different concentrations contributes to the deduction of breakdown voltage. When the electric field strength along the bridge lines exceeded the critical electric field strength of the oil, instantaneous breakdown was initiated and established only at a certain impulse stress level. In addition, cellulose particles tended to accumulate and form a thin bridge skeleton at respective of non-breakdown of impulse shot. Although the cellulose particles bridged the gap, no breakdown occurred because the electric field did not exceed the critical field of CO. This finding potentially contributes to the formulation of guidelines for condition assessment and contamination monitoring to minimise common issues in power transformer failures that are attributable to the insulation system, and consequently, achieve optimum transformer insulation integrity.

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Streamer characteristic and breakdown in a mineral oil and a synthetic ester liquid under DC voltage

Cited by 18 publications

References 19 publications

Alternative Dielectric Fluids for Transformer Insulation System: Progress, Challenges, and Future Prospects

Alternative Dielectric Fluids for Transformer Insulation System: Progress, Challenges, and Future Prospects

A Review on Synthetic Ester Liquids for Transformer Applications

Breakdown Voltage of Transformer Oil Containing Cellulose Particle Contamination With and Without Bridge Formation Under Lightning Impulse Stress

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