Abstract: The use of vegetable oil (or natural ester) as an insulating fluid in electrical transformers is a trend that aims to contribute to environmental preservation since it is biodegradable and non-toxic. Besides, vegetable oil has high flash and combustion points, being considered a fire safety fluid. However, vegetable oil is usually less stable towards oxidation than mineral oil. Both insulating fluids, mineral and vegetable oils, need to be tested periodically according to specific standards. Oxidation stability can be determined by the induction period measured by conductivity method (Rancimat) by monitoring the effectivity of oil’s antioxidant additives, a methodology already developed for food application and biodiesel but still not standardized for insulating fluids. Besides adequate oxidation stability, fluids must be compatible with transformer's construction materials under normal operating conditions to ensure that damage to the oil and parts of the transformer does not occur. ASTM standard and Brazilian normative differ in parameters evaluated, which reveals the need to regulate tests for each oil type. The aim of this study was to assess oxidation stability and compatibility of vegetable oils to suggest the best way to assure a viable performance of vegetable oil as transformer insulating fluid. The determination of the induction period for several vegetable insulating oils from the local market by using Rancimat was carried out according to BS EN 14112 standard, at different temperatures (110, 120, and 130 °C). Also, the compatibility of vegetable oil was assessed according to ASTM and ABNT NBR standards. The main results showed that the best temperature for use in the Rancimat test is 130 °C, which allows a better observation of conductivity change. The compatibility test results presented differences between vegetable and mineral oil standards that should be taken into account in oil testing since materials compatibility and oxidation stability are essential for equipment reliability.
Abstract: Biodiesel is one of the alternative fuels that promising
for substituting petro diesel as energy source which is advantage on
sustainability and ecofriendly. Due to the raw material that tend to
decompose during storage, biodiesel also have the same characteristic
that tend to decompose and formed higher acid value which is the
result of oxidation to double bond on a chain of ester. Decomposition of biodiesel due to oxidation reaction could
prevent by introduce a small amount of antioxidant. The origin of raw
materials and the process for producing biodiesel will determine the
effectiveness of antioxidant. The quality degradation on biodiesel
could evaluate by measuring iodine value and acid number of
biodiesel. Biodiesel made from high fatty acid Jatropha curcas oil by using
esterification and transesterification process will stand on the quality
by introduce 90 ppm pyrogallol powder on the biodiesel, which could
increase Induction period time from 2 hours to more than 6 hours in
rancimat test evaluation.
Abstract: Application of synthetic antioxidants such as tertbutylhydroquinon
(TBHQ), in spite of their efficiency, is questioned
because of their possible carcinogenic effect. The purpose of this
study was application of mixtures of natural antioxidants that provide
the best oxidative stability for margarine. Antioxidant treatments
included 10 various mixtures (F1- F10) containing 100-500ppm
tocopherol mixture (Toc), 100-200ppm ascorbyl palmitate (AP), 100-
200ppm rosemary extract (Ros) and 1000ppm lecithin(Lec) along
with a control or F0 (with no antioxidant) and F11 with 120ppm
TBHQ. The effect of antioxidant mixtures on the stability of
margarine samples during oven test (60°C), rancimat test at 110°C
and storage at 4°C was evaluated. Final ranking of natural antioxidant
mixtures was as follows: F2,F10>F5,F9>F8>F1,F3,F4>F6, F7.
Considering the results of this research and ranking criteria,
F2(200ppmAp + 200ppmRos) and F10(200ppmRos + 200ppmToc
+1000ppmLec) were recommended as substitutes for TBHQ to
maintain the quality and increase the shelf-life of margarine.
Abstract: Milk from differently fed cows (supplemented with carotenoids from carrots or palm oil product Carotino CAF 100) was obtained in a conventional dairy farm to assess the carotenoid potential to protect milk fat against oxidation. The extracted anhydrous milk fat (AMF) was tested by peroxide value, and Rancimat tests. Temperature, and light stimulation for reaction acceleration was used. The oxidative stability enhancement by carotenoids was detected in peroxide value test – the strongest effect was observed in palm oil, following by carrot supplemented group, compared to control group, whose feed was unchanged. Rancimat accelerated oxidation test results did not show any superiority of the oxidative stability of the AMF samples from milk of the carotenoidsupplemented cow groups. The average oxidation stability of AMF dark-stored samples was 12.59 ± 0.294 h, and it was significantly (p < 0.05) higher than that of AMF light-affected samples, i.e. 2.60 ± 0.191 h.