NDLI: Light-matter interaction in transformer oil

Content Provider	IEEE Xplore Digital Library
Author	Namihira, T. Wang, D. Neuber, A. Butcher, M. Dickens, J. Krompholz, H.
Copyright Year	2004
Description	Author affiliation: Kumamoto Univ., Japan (Namihira, T.; Wang, D.)
Abstract	Summary form only given. Considering highly stressed dielectric liquids, the role of mechanisms such as photoionization in the liquid volume or photoeffect at the cathode for the development of dielectric breakdown is investigated. We used a pulsed 300 W Xenon light source (25 mm output window, 5 degree divergence) with a broad spectral range of 200 to 1100 nm to study the impact of the light beam focused either solely on the high field region between the breakdown electrodes or including the electrodes. Typical field strengths in the electrode gap (/spl sim/4 mm gap, 3 mm tip radius,) were 15 to 25 kV/cm resulting in a DC current amplitude (without light) of up to 2 nA (apparatus resolution /spl sim/10 pA). Standard transformer oil, Univolt 61, and a biodegradable oil, Environtemp FR3 (natural ester fluid), were examined in the present work. Both oils exhibit strong optical absorption in the UV. However, Univolt 61 has its cut off wavelength at 450 nm, while bio oil easily transmits down to 350 nm. Below the cutoff wavelength, virtually all radiation is absorbed within a few mm. When pulsing the Xenon lamp at /spl sim/500 microsec no increase in DC current amplitude (increase <10 pA) could be detected for either oil. Increasing the pulse length to several seconds lead to a distinct increase in current amplitude (up to 300 pA), however, only for Univolt 61. Such an increase in current amplitude can also be achieved by raising the temperature of the dielectric liquid by external heating (/spl sim/100 pA/K). The temperature levels leading to similar current amplitudes due to heating by the Xenon lamp or external heating are comparable. Since bio oil absorbs only below 350 nm, the temperature rise due to the light irradiation was comparably smaller than in Univolt 61. Thus, any heating and increase in current were less pronounced in bio oil. For both oils, the observed behavior can be entirely explained by thermal effects. Both, photoionization and photoeffect have seemingly a minor impact on breakdown development. The detailed discussions are given in the present work.
Sponsorship	Plasma Sci. and Applications Committee of the IEEE Nuclear and Plasma Sci. Soc
File Size	78298
File Format	PDF
ISBN	0780383346
ISSN	07309244
DOI	10.1109/PLASMA.2004.1340266
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2004-07-01
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Oil insulation Petroleum Heating Xenon Electrodes Temperature Dielectric liquids Ionization Electric breakdown Lamps
Content Type	Text
Resource Type	Article
Subject	Atomic and Molecular Physics, and Optics Condensed Matter Physics Electrical and Electronic Engineering

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