Lightning Impulse Withstand of Natural Ester Liquid

Stephanie Haegele, Farzaneh Vahidi, Stefan Tenbohlen, Kevin J. Rapp and Alan Sbravati
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Stephanie Haegele: Institute of Power Transmission and High Voltage Technology, University of Stuttgart, 70569 Stuttgart, Germany
Farzaneh Vahidi: Institute of Power Transmission and High Voltage Technology, University of Stuttgart, 70569 Stuttgart, Germany
Stefan Tenbohlen: Institute of Power Transmission and High Voltage Technology, University of Stuttgart, 70569 Stuttgart, Germany
Kevin J. Rapp: Cargill Inc., Cargill Industrial Specialties—Dielectric Fluids, Plymouth, MN 55441, USA
Alan Sbravati: Cargill Inc., Cargill Industrial Specialties—Dielectric Fluids, Plymouth, MN 55441, USA

Energies, 2018, vol. 11, issue 8, 1-13

Abstract: 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.

Keywords: dielectric breakdown voltage; dielectric liquids; natural ester liquids vs. mineral oil; power transformers; vegetable oils (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
References: View complete reference list from CitEc
Citations: View citations in EconPapers (5)

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