Dielectric response of oil-impregnated cellulose from 0.1 mHz to 3 MHz

Pressboard and Kraft paper with and without moisture, with and without added acids have been tested with frequency domain spectroscopy up to 1 kHz. Kraft paper with three moisture levels has also been tested at various ageing levels. Moisture and low-molecular carboxylic acids cause shifts in the pe...

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Bibliographic Details
Main Authors: Linhjell, D., Hestad, O.L., Gafvert, U., Lundgaard, L.E.
Format: Conference Proceeding
Language:English
Subjects:
Aging
Dielectrics
Frequency
Magnetic field measurement
Moisture
Permittivity measurement
Petroleum
Polymers
Testing
Transformers
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Summary:Pressboard and Kraft paper with and without moisture, with and without added acids have been tested with frequency domain spectroscopy up to 1 kHz. Kraft paper with three moisture levels has also been tested at various ageing levels. Moisture and low-molecular carboxylic acids cause shifts in the permittivity vs. frequency curves. In addition, in paper but not pressboard, moisture is associated with an extra relaxation in the low-frequency part. High-molecular carboxylic acids have little effect on the permittivity. The same is the case for reduction in chain length of the cellulose polymer. The method should be useful as a non-invasive field test method for destructive agents in transformers, but not for the ageing (chain scission) itself. The measurements up to 3 MHz are so far inconclusive, but have yielded a few results that blend in well with the measurements below 1 kHz.
ISSN:2153-3725
2153-3733
DOI:10.1109/ICDL.2005.1490080