Title :
Dielectric response of oil-impregnated cellulose from 0.1 mHz to 3 MHz
Author :
Linhjell, D. ; Hestad, O.L. ; Gäfvert, U. ; Lundgaard, L.E.
Author_Institution :
SINTEF Energy Res., Trondheim, Norway
Abstract :
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.
Keywords :
ageing; filled polymers; inorganic compounds; moisture; oils; paper; permittivity; 0.1 mHz to 3 MHz; Kraft paper; ageing levels; cellulose polymer; chain length; dielectric response; frequency curves; frequency domain spectroscopy; low-molecular carboxylic acids; moisture levels; oil-impregnated cellulose; permittivity; pressboard; Aging; Dielectrics; Frequency; Magnetic field measurement; Moisture; Permittivity measurement; Petroleum; Polymers; Testing; Transformers;
Conference_Titel :
Dielectric Liquids, 2005. ICDL 2005. 2005 IEEE International Conference on
Print_ISBN :
0-7803-8954-9
DOI :
10.1109/ICDL.2005.1490080