Suwarno, Aminudin S.
Ester, Kraft paper, Dissolved Gas Analysis, dielectric properties, SEM, EDS
Since long time ago, mineral oil is being used as insulation for high voltage equipments such as transformers. Due to environment consideration and the long term availability, liquid insulation from plantation are being introduced. However, the performance of such insulation in composite with paper should be investigated in order to maintain the quality of the insulation in operating equipments under electric and thermal stresses. This paper reports the experimental results on the effects of thermal aging of natural ester from palm oil and Kraft paper composite insulation. Samples of 800 ml ester and 6 gram of kraft insulation paper were put together in heat-resistant hermetic bottles to simulate actual condition of transformator. All samples were subjected to thermal aging condition for duration of 336 hours to 672 hours at 120oC and 150oC in a controllable oven. Dielectric properties such as breakdown voltage, resistivity, water content were measured and dissolved gas analysis were conducted after and before aging. The morphological aging of the kraft paper was investigated using SEM (scanning electron microscopy) while chemical element change was investigated using EDS (energy dispersive spectroscopy). The experimental results indicated that thermal aging process greatly affected the breakdown voltage and resistivity. At initial stage of thermal aging application the breakdown voltage increased due to the reduction of water content. However, long term aging reduced the breakdown voltage due to the drastic increase of oxidation by product which was indicated by the darker color. Dissolved gas analysis indicated that thermal aging in ester-paper composite insulation released H2 (Hydrogen), CH4 (Methane), C2H2 (Acetylene), C2H4 (ethylene), C2H6 (ethane), and CO (Carbon Monoxide). The EDS analysis showed that during aging the C element increased while O element decreased. EDS data of krafft paper aged at 120oC for a duration of 4 weeks (672 hours) taken using JEOL 6510 at accelerated voltage of 10 kV with energy range of 0-20 keV showed that the aged paper consists of 3 elements, C , O and K elements with mass percentage of 75.23 % of C at energy of 0.277 keV , O of 21.69 % observed at energy of 0.525 keV and new element of K with mass percentage of 3.08 observed at energy of 3.312 keV. It is clearly observed that C increased from 58.83 % to 75.23 %. This is due to the migration from the ester into the paper on the other hand oxygen reduced from 41.17 % to 21.69 % because the oxygen from the paper reacted with oil in an oxidation and release CO gas as confirmed by DGA (dissolved gas analysis). Similar behavior was observed for aging at 150oC.
Cite this paper
Suwarno, Aminudin S.. (2016) Thermal Aging of Ester from Palm Oil and Kraft Paper Composite Insulation. International Journal of Applied Physics, 1, 77-84