Characterization of inhomogeneous field breakdown in natural ester liquid compared to mineral oil

Haegele, S.; Tenbohlen, Stefan; Fritsche, Ronny; Rapp, Kevin; Sbravati, Alan

doi:10.1109/ichve.2016.7800900

Cited by 9 publications

(17 citation statements)

References 5 publications

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“…As surface defects are the dominant breakdown effect during LI stress [17], electrode surface effects need to be considered and tested before the actual investigation. Preliminary tests were conducted to define electrode replacement intervals and polishing intervals [18].…”

Section: Electrode Conditioningmentioning

confidence: 99%

“…Needles were electrically tested at different stress levels: No stress, one impulse, 10 impulses, 15 impulses, one breakdown and several breakdowns. Results and scanning electron microscope images can be found in [18]. ASTM D3300 standard with which mentioned investigations were performed suggests electrode polishing intervals of five breakdowns for sphere electrodes and immediate replacement of needle electrodes after one breakdown.…”

Section: Electrode Conditioningmentioning

confidence: 99%

“…Blunt points with larger radii could be polished several times. Corresponding polishing intervals can be found in [18].…”

Section: Electrode Conditioningmentioning

confidence: 99%

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Lightning Impulse Withstand of Natural Ester Liquid

et al. 2018

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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.

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Section: Electrode Conditioningmentioning

confidence: 99%

Section: Electrode Conditioningmentioning

confidence: 99%

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Lightning Impulse Withstand of Natural Ester Liquid

et al. 2018

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“…There are many studies evaluating the breakdown voltages of insulation liquids for different configurations of electrodes. [2][3][4][5][6][7][8] In the research of Thien et al, 2 breakdown voltages of palm oil and mineral oil were measured with point-spherical and point-plane electrode systems. The lowest breakdown voltages were obtained with the latter since the more severe electric fields were generated.…”

Section: Literature Overviewmentioning

confidence: 99%

Analysis of breakdown mechanism based on contact area and field enhancement factor of different electrode‐material combinations

Akin

Arıkan

2022

Intl J of Energy Research

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In this study, the effect of electrode configurations on breakdown performances of polyethylene terephthalate, presspaper and styrene-butadiene rubber/natural rubber blend is investigated with the considerations of electrode area and field enhancement factor. Cylinder-cylinder, spherical-cylinder and point-cylinder electrode configurations are used for breakdown experiments and the measurements are taken according to the rapid-rise method. Characteristic breakdown voltages of the materials are obtained for each electrode configuration by performing Weibull analysis on experimental results. Based

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“…Before vegetable oils can be accepted as an alternative to MO, they must be safe, economical and offer a high standard of electrical properties over the transformer lifespan. Recently, extensive works were carried out to investigate the suitability of vegetable oils as the alternative to MO [12][13][14][15][16][17][18]. The studies evaluated dielectric properties, physical and chemical performances under different conditions and ageing properties.…”

Section: Introductionmentioning

confidence: 99%

Lightning Impulse Breakdown Voltage of Rice Bran Oil for Transformer Application

et al. 2021

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Transformer oil does not only serve as an insulating liquid, but also in removing heat from the windings and cores. Mineral oil (MO) has been widely used in transformers for more than 150 years. Recently, researchers have attempted to search for alternative insulating oils due to the possibility that MO will run out in the future together with the concern on fire safety and environmental pollution. Among the potential oils is rice bran oil (RBO). This work presents the studies of the lightning impulse (LI) of RBO behavior under various electric fields, gap distances and testing methods. The electrical performances of LI tests show that RBO and Palm Oil (PO) have lower LI breakdown voltage than MO under both uniform and non-uniform electric fields. However, the difference in LI breakdown voltages between RBO, PO and MO are slightly small which is less than 20%. In addition, there is no significant effect in the various testing methods under both uniform field and non-uniform field where the percentages of difference are less than 12% and 8% respectively. The data of LI breakdown voltage were statistically analysed to predict the withstand voltage and 50% breakdown voltage of oil samples by using Weibull distribution. The Weibull distribution of MO, PO and RBO has well fit with the fitting line. Finally, the relationship between LI voltages under a non-uniform field with various parameters of PO and RBO was obtained and proposed. From this work, it can be concluded that RBO shows promising results to be considered as an alternative to MO in transformer applications.

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Characterization of inhomogeneous field breakdown in natural ester liquid compared to mineral oil

Cited by 9 publications

References 5 publications

Lightning Impulse Withstand of Natural Ester Liquid

Lightning Impulse Withstand of Natural Ester Liquid

Analysis of breakdown mechanism based on contact area and field enhancement factor of different electrode‐material combinations

Lightning Impulse Breakdown Voltage of Rice Bran Oil for Transformer Application

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